Atoms and Molecules

educat Atoms and molecules an atom and its structure Atoms are made up of particles of matter known as subatomic or fundamental particles. The three main subatomic particles are called protons, neutrons and electrons. An atom consists mostly of empty space. Almost all of the atom's mass is concentrated in a structure at its centre called the nucleus. The nucleus consists of protons and neutrons grouped together. Electrons orbit the nucleus. An electron is a negatively charged particle. It is kept in orbit around the nucleus because it is attracted to the positively charged protons. This attraction holds the atom together. An electron's mass is approximately 1840 times smaller than the mass of a proton or neutron. A proton is a positively charged particle A neutron has no electric charge Protons and neutrons have almost the same masses An atom usually contains an equal number of positively charged protons and negatively charged electrons. This makes it electrically neutral. electrons and their energy levels molecules The way in which an atom reacts with other atoms (its chemical properties) is determined by the configuration of its electrons. Atoms can gain, lose or share electrons when they combine to form molecules. The electrons in an atom exist in layers called energy levels or shells. Electrons are arranged in the energy levels according to certain rules: While an atom is the smallest particle of an element, molecules are the smallest particles of a compound. A molecule is formed when at least two atoms combine. These may be of the same element, or of different elements. If the atoms in a molecule are of different elements, it is called a compound. An example of such a compound is the carbon dioxide molecule: The first shell outside the nucleus holds up to two electrons CO, one carbon atom carbon dioxide molecule The third shell holds up to eight electrons. two oxygen atoms The second shell holds up to eight electrons A carbon atom has 4 electrons on its outer shell, while an oxygen atom has 6 electrons on its outer shell. It is thus necessary for 2 oxygen atoms to bond with 1 carbon atom so that the 2 oxygen atoms can fill their outer shells with 2 electrons, respectively, from the carbon atom ensuring that both oxygen atoms have full outer shells (8 required for 2nd shell) as does the carbon atom (2 required for 1st shell). When a shell is full, a new one is started. The atomic number of an element tells you how many electrons that element has. An atom has as many energy levels as it needs to arrange its electrons. The number of electrons in the outer energy level determines how reactive an atom is. Atoms like their energy levels to be full. The most stable atoms are those with full outer energy levels, like helium. The most reactive atoms, like sodium, are those that only need to lose or gain one electron to obtain a full outer shell. Atomic Number 13 Number of electrons per energy level (electron configuration) Atomic Symbol Atomic Mass Aluminum 26.981538 compounds & formulae Compounds are formed when different elements combine. Like elements, each compound has a name and a symbol. The symbol of a compound is made of the symbols of the elements which form it, and is called a formula. A formula is used to show the atoms in a molecule. The numbers in a formula give the number of atoms of each kind of element in the molecule. The number of atoms of each element in that molecule is written after the symbol of the element, in small letters below the line e.g. O' which is a molecule of oxygen. A number written immediately before the formula of a molecule tells you how many molecules there are. differences between mixtures & compounds MIXTURES (e.g. iron and sulphur) *impure substances *the proportions of the parts can vary (change) *the components can be elements or compounds *the components are loosely put together *the properties of each part do not change *the properties of the mixture are the same as the properties of all its parts. COMPOUNDS (e.g. iron sulphide) *pure substances *the proportions of the parts are constant *the components are elements *the components are held together by chemical bonds. *the properties of the compound are different from the properties of the elements forming it, and from a mixture of these elements. The mixture formed when one substance dissolves into another is called a solution. Sugar that is dissolved in water is a solution. There are always two parts of a solution: the solute and the solvent. The component which forms the greatest part of the solution is the solvent. Water is the solvent of the sugar solution. The sugar is the solute. This number shows that there are 2M9CI, these are joined by chemical bonds to form one molecule of magnesium chloride two atoms of chlorine two molecules of magnesium chloride one atom of magnesium Approved by the European Community for quality and safety. Published and distributed by Educat Ltd, Cape Town, South Africa. All rights reserved. Copyright © 1995 Educat Ltd. Fax: 27(21) 434 4106 E-mail: [email protected] Website: www.educat.co.za CE educat Atoms and molecules an atom and its structure Atoms are made up of particles of matter known as subatomic or fundamental particles. The three main subatomic particles are called protons, neutrons and electrons. An atom consists mostly of empty space. Almost all of the atom's mass is concentrated in a structure at its centre called the nucleus. The nucleus consists of protons and neutrons grouped together. Electrons orbit the nucleus. An electron is a negatively charged particle. It is kept in orbit around the nucleus because it is attracted to the positively charged protons. This attraction holds the atom together. An electron's mass is approximately 1840 times smaller than the mass of a proton or neutron. A proton is a positively charged particle A neutron has no electric charge Protons and neutrons have almost the same masses An atom usually contains an equal number of positively charged protons and negatively charged electrons. This makes it electrically neutral. electrons and their energy levels molecules The way in which an atom reacts with other atoms (its chemical properties) is determined by the configuration of its electrons. Atoms can gain, lose or share electrons when they combine to form molecules. The electrons in an atom exist in layers called energy levels or shells. Electrons are arranged in the energy levels according to certain rules: While an atom is the smallest particle of an element, molecules are the smallest particles of a compound. A molecule is formed when at least two atoms combine. These may be of the same element, or of different elements. If the atoms in a molecule are of different elements, it is called a compound. An example of such a compound is the carbon dioxide molecule: The first shell outside the nucleus holds up to two electrons CO, one carbon atom carbon dioxide molecule The third shell holds up to eight electrons. two oxygen atoms The second shell holds up to eight electrons A carbon atom has 4 electrons on its outer shell, while an oxygen atom has 6 electrons on its outer shell. It is thus necessary for 2 oxygen atoms to bond with 1 carbon atom so that the 2 oxygen atoms can fill their outer shells with 2 electrons, respectively, from the carbon atom ensuring that both oxygen atoms have full outer shells (8 required for 2nd shell) as does the carbon atom (2 required for 1st shell). When a shell is full, a new one is started. The atomic number of an element tells you how many electrons that element has. An atom has as many energy levels as it needs to arrange its electrons. The number of electrons in the outer energy level determines how reactive an atom is. Atoms like their energy levels to be full. The most stable atoms are those with full outer energy levels, like helium. The most reactive atoms, like sodium, are those that only need to lose or gain one electron to obtain a full outer shell. Atomic Number 13 Number of electrons per energy level (electron configuration) Atomic Symbol Atomic Mass Aluminum 26.981538 compounds & formulae Compounds are formed when different elements combine. Like elements, each compound has a name and a symbol. The symbol of a compound is made of the symbols of the elements which form it, and is called a formula. A formula is used to show the atoms in a molecule. The numbers in a formula give the number of atoms of each kind of element in the molecule. The number of atoms of each element in that molecule is written after the symbol of the element, in small letters below the line e.g. O' which is a molecule of oxygen. A number written immediately before the formula of a molecule tells you how many molecules there are. differences between mixtures & compounds MIXTURES (e.g. iron and sulphur) *impure substances *the proportions of the parts can vary (change) *the components can be elements or compounds *the components are loosely put together *the properties of each part do not change *the properties of the mixture are the same as the properties of all its parts. COMPOUNDS (e.g. iron sulphide) *pure substances *the proportions of the parts are constant *the components are elements *the components are held together by chemical bonds. *the properties of the compound are different from the properties of the elements forming it, and from a mixture of these elements. The mixture formed when one substance dissolves into another is called a solution. Sugar that is dissolved in water is a solution. There are always two parts of a solution: the solute and the solvent. The component which forms the greatest part of the solution is the solvent. Water is the solvent of the sugar solution. The sugar is the solute. This number shows that there are 2M9CI, these are joined by chemical bonds to form one molecule of magnesium chloride two atoms of chlorine two molecules of magnesium chloride one atom of magnesium Approved by the European Community for quality and safety. Published and distributed by Educat Ltd, Cape Town, South Africa. All rights reserved. Copyright © 1995 Educat Ltd. Fax: 27(21) 434 4106 E-mail: [email protected] Website: www.educat.co.za CE educat Atoms and molecules an atom and its structure Atoms are made up of particles of matter known as subatomic or fundamental particles. The three main subatomic particles are called protons, neutrons and electrons. An atom consists mostly of empty space. Almost all of the atom's mass is concentrated in a structure at its centre called the nucleus. The nucleus consists of protons and neutrons grouped together. Electrons orbit the nucleus. An electron is a negatively charged particle. It is kept in orbit around the nucleus because it is attracted to the positively charged protons. This attraction holds the atom together. An electron's mass is approximately 1840 times smaller than the mass of a proton or neutron. A proton is a positively charged particle A neutron has no electric charge Protons and neutrons have almost the same masses An atom usually contains an equal number of positively charged protons and negatively charged electrons. This makes it electrically neutral. electrons and their energy levels molecules The way in which an atom reacts with other atoms (its chemical properties) is determined by the configuration of its electrons. Atoms can gain, lose or share electrons when they combine to form molecules. The electrons in an atom exist in layers called energy levels or shells. Electrons are arranged in the energy levels according to certain rules: While an atom is the smallest particle of an element, molecules are the smallest particles of a compound. A molecule is formed when at least two atoms combine. These may be of the same element, or of different elements. If the atoms in a molecule are of different elements, it is called a compound. An example of such a compound is the carbon dioxide molecule: The first shell outside the nucleus holds up to two electrons CO, one carbon atom carbon dioxide molecule The third shell holds up to eight electrons. two oxygen atoms The second shell holds up to eight electrons A carbon atom has 4 electrons on its outer shell, while an oxygen atom has 6 electrons on its outer shell. It is thus necessary for 2 oxygen atoms to bond with 1 carbon atom so that the 2 oxygen atoms can fill their outer shells with 2 electrons, respectively, from the carbon atom ensuring that both oxygen atoms have full outer shells (8 required for 2nd shell) as does the carbon atom (2 required for 1st shell). When a shell is full, a new one is started. The atomic number of an element tells you how many electrons that element has. An atom has as many energy levels as it needs to arrange its electrons. The number of electrons in the outer energy level determines how reactive an atom is. Atoms like their energy levels to be full. The most stable atoms are those with full outer energy levels, like helium. The most reactive atoms, like sodium, are those that only need to lose or gain one electron to obtain a full outer shell. Atomic Number 13 Number of electrons per energy level (electron configuration) Atomic Symbol Atomic Mass Aluminum 26.981538 compounds & formulae Compounds are formed when different elements combine. Like elements, each compound has a name and a symbol. The symbol of a compound is made of the symbols of the elements which form it, and is called a formula. A formula is used to show the atoms in a molecule. The numbers in a formula give the number of atoms of each kind of element in the molecule. The number of atoms of each element in that molecule is written after the symbol of the element, in small letters below the line e.g. O' which is a molecule of oxygen. A number written immediately before the formula of a molecule tells you how many molecules there are. differences between mixtures & compounds MIXTURES (e.g. iron and sulphur) *impure substances *the proportions of the parts can vary (change) *the components can be elements or compounds *the components are loosely put together *the properties of each part do not change *the properties of the mixture are the same as the properties of all its parts. COMPOUNDS (e.g. iron sulphide) *pure substances *the proportions of the parts are constant *the components are elements *the components are held together by chemical bonds. *the properties of the compound are different from the properties of the elements forming it, and from a mixture of these elements. The mixture formed when one substance dissolves into another is called a solution. Sugar that is dissolved in water is a solution. There are always two parts of a solution: the solute and the solvent. The component which forms the greatest part of the solution is the solvent. Water is the solvent of the sugar solution. The sugar is the solute. This number shows that there are 2M9CI, these are joined by chemical bonds to form one molecule of magnesium chloride two atoms of chlorine two molecules of magnesium chloride one atom of magnesium Approved by the European Community for quality and safety. Published and distributed by Educat Ltd, Cape Town, South Africa. All rights reserved. Copyright © 1995 Educat Ltd. Fax: 27(21) 434 4106 E-mail: [email protected] Website: www.educat.co.za CE educat Atoms and molecules an atom and its structure Atoms are made up of particles of matter known as subatomic or fundamental particles. The three main subatomic particles are called protons, neutrons and electrons. An atom consists mostly of empty space. Almost all of the atom's mass is concentrated in a structure at its centre called the nucleus. The nucleus consists of protons and neutrons grouped together. Electrons orbit the nucleus. An electron is a negatively charged particle. It is kept in orbit around the nucleus because it is attracted to the positively charged protons. This attraction holds the atom together. An electron's mass is approximately 1840 times smaller than the mass of a proton or neutron. A proton is a positively charged particle A neutron has no electric charge Protons and neutrons have almost the same masses An atom usually contains an equal number of positively charged protons and negatively charged electrons. This makes it electrically neutral. electrons and their energy levels molecules The way in which an atom reacts with other atoms (its chemical properties) is determined by the configuration of its electrons. Atoms can gain, lose or share electrons when they combine to form molecules. The electrons in an atom exist in layers called energy levels or shells. Electrons are arranged in the energy levels according to certain rules: While an atom is the smallest particle of an element, molecules are the smallest particles of a compound. A molecule is formed when at least two atoms combine. These may be of the same element, or of different elements. If the atoms in a molecule are of different elements, it is called a compound. An example of such a compound is the carbon dioxide molecule: The first shell outside the nucleus holds up to two electrons CO, one carbon atom carbon dioxide molecule The third shell holds up to eight electrons. two oxygen atoms The second shell holds up to eight electrons A carbon atom has 4 electrons on its outer shell, while an oxygen atom has 6 electrons on its outer shell. It is thus necessary for 2 oxygen atoms to bond with 1 carbon atom so that the 2 oxygen atoms can fill their outer shells with 2 electrons, respectively, from the carbon atom ensuring that both oxygen atoms have full outer shells (8 required for 2nd shell) as does the carbon atom (2 required for 1st shell). When a shell is full, a new one is started. The atomic number of an element tells you how many electrons that element has. An atom has as many energy levels as it needs to arrange its electrons. The number of electrons in the outer energy level determines how reactive an atom is. Atoms like their energy levels to be full. The most stable atoms are those with full outer energy levels, like helium. The most reactive atoms, like sodium, are those that only need to lose or gain one electron to obtain a full outer shell. Atomic Number 13 Number of electrons per energy level (electron configuration) Atomic Symbol Atomic Mass Aluminum 26.981538 compounds & formulae Compounds are formed when different elements combine. Like elements, each compound has a name and a symbol. The symbol of a compound is made of the symbols of the elements which form it, and is called a formula. A formula is used to show the atoms in a molecule. The numbers in a formula give the number of atoms of each kind of element in the molecule. The number of atoms of each element in that molecule is written after the symbol of the element, in small letters below the line e.g. O' which is a molecule of oxygen. A number written immediately before the formula of a molecule tells you how many molecules there are. differences between mixtures & compounds MIXTURES (e.g. iron and sulphur) *impure substances *the proportions of the parts can vary (change) *the components can be elements or compounds *the components are loosely put together *the properties of each part do not change *the properties of the mixture are the same as the properties of all its parts. COMPOUNDS (e.g. iron sulphide) *pure substances *the proportions of the parts are constant *the components are elements *the components are held together by chemical bonds. *the properties of the compound are different from the properties of the elements forming it, and from a mixture of these elements. The mixture formed when one substance dissolves into another is called a solution. Sugar that is dissolved in water is a solution. There are always two parts of a solution: the solute and the solvent. The component which forms the greatest part of the solution is the solvent. Water is the solvent of the sugar solution. The sugar is the solute. This number shows that there are 2M9CI, these are joined by chemical bonds to form one molecule of magnesium chloride two atoms of chlorine two molecules of magnesium chloride one atom of magnesium Approved by the European Community for quality and safety. Published and distributed by Educat Ltd, Cape Town, South Africa. All rights reserved. Copyright © 1995 Educat Ltd. Fax: 27(21) 434 4106 E-mail: [email protected] Website: www.educat.co.za CE educat Atoms and molecules an atom and its structure Atoms are made up of particles of matter known as subatomic or fundamental particles. The three main subatomic particles are called protons, neutrons and electrons. An atom consists mostly of empty space. Almost all of the atom's mass is concentrated in a structure at its centre called the nucleus. The nucleus consists of protons and neutrons grouped together. Electrons orbit the nucleus. An electron is a negatively charged particle. It is kept in orbit around the nucleus because it is attracted to the positively charged protons. This attraction holds the atom together. An electron's mass is approximately 1840 times smaller than the mass of a proton or neutron. A proton is a positively charged particle A neutron has no electric charge Protons and neutrons have almost the same masses An atom usually contains an equal number of positively charged protons and negatively charged electrons. This makes it electrically neutral. electrons and their energy levels molecules The way in which an atom reacts with other atoms (its chemical properties) is determined by the configuration of its electrons. Atoms can gain, lose or share electrons when they combine to form molecules. The electrons in an atom exist in layers called energy levels or shells. Electrons are arranged in the energy levels according to certain rules: While an atom is the smallest particle of an element, molecules are the smallest particles of a compound. A molecule is formed when at least two atoms combine. These may be of the same element, or of different elements. If the atoms in a molecule are of different elements, it is called a compound. An example of such a compound is the carbon dioxide molecule: The first shell outside the nucleus holds up to two electrons CO, one carbon atom carbon dioxide molecule The third shell holds up to eight electrons. two oxygen atoms The second shell holds up to eight electrons A carbon atom has 4 electrons on its outer shell, while an oxygen atom has 6 electrons on its outer shell. It is thus necessary for 2 oxygen atoms to bond with 1 carbon atom so that the 2 oxygen atoms can fill their outer shells with 2 electrons, respectively, from the carbon atom ensuring that both oxygen atoms have full outer shells (8 required for 2nd shell) as does the carbon atom (2 required for 1st shell). When a shell is full, a new one is started. The atomic number of an element tells you how many electrons that element has. An atom has as many energy levels as it needs to arrange its electrons. The number of electrons in the outer energy level determines how reactive an atom is. Atoms like their energy levels to be full. The most stable atoms are those with full outer energy levels, like helium. The most reactive atoms, like sodium, are those that only need to lose or gain one electron to obtain a full outer shell. Atomic Number 13 Number of electrons per energy level (electron configuration) Atomic Symbol Atomic Mass Aluminum 26.981538 compounds & formulae Compounds are formed when different elements combine. Like elements, each compound has a name and a symbol. The symbol of a compound is made of the symbols of the elements which form it, and is called a formula. A formula is used to show the atoms in a molecule. The numbers in a formula give the number of atoms of each kind of element in the molecule. The number of atoms of each element in that molecule is written after the symbol of the element, in small letters below the line e.g. O' which is a molecule of oxygen. A number written immediately before the formula of a molecule tells you how many molecules there are. differences between mixtures & compounds MIXTURES (e.g. iron and sulphur) *impure substances *the proportions of the parts can vary (change) *the components can be elements or compounds *the components are loosely put together *the properties of each part do not change *the properties of the mixture are the same as the properties of all its parts. COMPOUNDS (e.g. iron sulphide) *pure substances *the proportions of the parts are constant *the components are elements *the components are held together by chemical bonds. *the properties of the compound are different from the properties of the elements forming it, and from a mixture of these elements. The mixture formed when one substance dissolves into another is called a solution. Sugar that is dissolved in water is a solution. There are always two parts of a solution: the solute and the solvent. The component which forms the greatest part of the solution is the solvent. Water is the solvent of the sugar solution. The sugar is the solute. This number shows that there are 2M9CI, these are joined by chemical bonds to form one molecule of magnesium chloride two atoms of chlorine two molecules of magnesium chloride one atom of magnesium Approved by the European Community for quality and safety. Published and distributed by Educat Ltd, Cape Town, South Africa. All rights reserved. Copyright © 1995 Educat Ltd. Fax: 27(21) 434 4106 E-mail: [email protected] Website: www.educat.co.za CE educat Atoms and molecules an atom and its structure Atoms are made up of particles of matter known as subatomic or fundamental particles. The three main subatomic particles are called protons, neutrons and electrons. An atom consists mostly of empty space. Almost all of the atom's mass is concentrated in a structure at its centre called the nucleus. The nucleus consists of protons and neutrons grouped together. Electrons orbit the nucleus. An electron is a negatively charged particle. It is kept in orbit around the nucleus because it is attracted to the positively charged protons. This attraction holds the atom together. An electron's mass is approximately 1840 times smaller than the mass of a proton or neutron. A proton is a positively charged particle A neutron has no electric charge Protons and neutrons have almost the same masses An atom usually contains an equal number of positively charged protons and negatively charged electrons. This makes it electrically neutral. electrons and their energy levels molecules The way in which an atom reacts with other atoms (its chemical properties) is determined by the configuration of its electrons. Atoms can gain, lose or share electrons when they combine to form molecules. The electrons in an atom exist in layers called energy levels or shells. Electrons are arranged in the energy levels according to certain rules: While an atom is the smallest particle of an element, molecules are the smallest particles of a compound. A molecule is formed when at least two atoms combine. These may be of the same element, or of different elements. If the atoms in a molecule are of different elements, it is called a compound. An example of such a compound is the carbon dioxide molecule: The first shell outside the nucleus holds up to two electrons CO, one carbon atom carbon dioxide molecule The third shell holds up to eight electrons. two oxygen atoms The second shell holds up to eight electrons A carbon atom has 4 electrons on its outer shell, while an oxygen atom has 6 electrons on its outer shell. It is thus necessary for 2 oxygen atoms to bond with 1 carbon atom so that the 2 oxygen atoms can fill their outer shells with 2 electrons, respectively, from the carbon atom ensuring that both oxygen atoms have full outer shells (8 required for 2nd shell) as does the carbon atom (2 required for 1st shell). When a shell is full, a new one is started. The atomic number of an element tells you how many electrons that element has. An atom has as many energy levels as it needs to arrange its electrons. The number of electrons in the outer energy level determines how reactive an atom is. Atoms like their energy levels to be full. The most stable atoms are those with full outer energy levels, like helium. The most reactive atoms, like sodium, are those that only need to lose or gain one electron to obtain a full outer shell. Atomic Number 13 Number of electrons per energy level (electron configuration) Atomic Symbol Atomic Mass Aluminum 26.981538 compounds & formulae Compounds are formed when different elements combine. Like elements, each compound has a name and a symbol. The symbol of a compound is made of the symbols of the elements which form it, and is called a formula. A formula is used to show the atoms in a molecule. The numbers in a formula give the number of atoms of each kind of element in the molecule. The number of atoms of each element in that molecule is written after the symbol of the element, in small letters below the line e.g. O' which is a molecule of oxygen. A number written immediately before the formula of a molecule tells you how many molecules there are. differences between mixtures & compounds MIXTURES (e.g. iron and sulphur) *impure substances *the proportions of the parts can vary (change) *the components can be elements or compounds *the components are loosely put together *the properties of each part do not change *the properties of the mixture are the same as the properties of all its parts. COMPOUNDS (e.g. iron sulphide) *pure substances *the proportions of the parts are constant *the components are elements *the components are held together by chemical bonds. *the properties of the compound are different from the properties of the elements forming it, and from a mixture of these elements. The mixture formed when one substance dissolves into another is called a solution. Sugar that is dissolved in water is a solution. There are always two parts of a solution: the solute and the solvent. The component which forms the greatest part of the solution is the solvent. Water is the solvent of the sugar solution. The sugar is the solute. This number shows that there are 2M9CI, these are joined by chemical bonds to form one molecule of magnesium chloride two atoms of chlorine two molecules of magnesium chloride one atom of magnesium Approved by the European Community for quality and safety. Published and distributed by Educat Ltd, Cape Town, South Africa. All rights reserved. Copyright © 1995 Educat Ltd. Fax: 27(21) 434 4106 E-mail: [email protected] Website: www.educat.co.za CE