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Chemistry:Green, Periodic Table, sodium + chlorine → sodium chloride,…
Chemistry:Green
Acids take part in reactions in which salts are produced. In these reactions, the salt is formed by replacing the hydrogen ions in the acids with metal ions or ammonium ions.
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Metallic bonding occurs between the atoms of metal elements - Lithium, Beryllium, Sodium, Magnesium, Aluminium and Calcium. The outer electrons are delocalised (free to move).
This produces an electrostatic force of attraction between the positive metal ions and the negative delocalised electrons.
This delocalised 'sea of electrons' is responsible for metal elements being able to conduct electricity.
Atoms can be held together by chemical bonds. When atoms form bonds, they can achieve a stable electron arrangement. To achieve a stable electron arrangement atoms can lose, gain or share electrons.
When metals react with other substances, the metal atoms lose electrons to form positive ions.
The reactivity series of metals is a chart showing metals in order of decreasing reactivity. In general, the more reactive a metal is:
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Ionic substances contain charged particles called ions. For example, lead bromide contains positively charged lead ions and negatively charged bromide ions.
Electrolysis is the process by which ionic substances are decomposed (broken down) into simpler substances when an electric current is passed through them.
Electricity is the flow of electrons or ions. For electrolysis to work, the compound must contain ions. Covalent compounds cannot act as electrolytes because they contain neutral atoms.
The ions must be free to move, which is possible when an ionic substance is dissolved in water or it is melted. For example, if electricity is passed through molten lead bromide, the lead bromide is broken down to form lead and bromine.
The table is called the periodic table because elements with similar properties occur at regular intervals.
elements with similar properties are placed in vertical columns, called groups
elements are arranged in rows, called periods, in order of increasing atomic number
Chemical amounts are measured in moles. The symbol for the unit mole is mol. The mass of one mole of a substance in grams is numerically equal to its relative formula mass. One mole of a substance contains the same number of the stated particles, atoms, molecules or ions as one mole of any other substance.
3 states of matter: Solid (s), Liquid (l), Gas (g)
Covalent bonding: A covalent bond forms when two non-metal atoms share a pair of electrons. The electrons involved are in the outer shells of the atoms. An atom that shares one or more of its electrons will complete its outer shell.
Covalent bonds are strong – a lot of energy is needed to break them. Substances with covalent bonds often form molecules with low melting and boiling points, such as hydrogen and water. These substances have strong covalent bonds within the molecules (between the atoms), but weak intermolecular forces between the molecules. This means that only a small amount of heat energy is required to separate the molecules from each other.
Structure and bonding
each carbon atom is joined to three other carbon atoms by covalent bonds. the carbon atoms form a hexagonal layered network structure. the layers have weak forces between them and can slide over each other. each carbon atom has one non-bonding outer electron.
Exothermic reactions are chemical reactions which release energy from the chemicals into the surroundings. This energy is usually released as heat, so the surroundings get hotter. Handwarmers are an example of an exothermic reaction. They release heat into their surroundings.
However, exothermic reactions don't always release heat, sometimes the energy is released as light. For example, glowsticks release light without increasing in temperature.
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In all of these reactions, the metal atoms give electrons to the non-metal atoms. The metal atoms become positive ions and the non-metal atoms become negative ions.
There is a strong electrostatic force of attraction between these oppositely charged ions – this is called an ionic bond.
When metals react with non-metals, electrons are transferred from the metal atoms to the non-metal atoms, forming ions. The resulting compound is called an ionic compound.
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Endothermic reactions absorb energy from the surroundings. This energy is usually absorbed as heat, so the surroundings get colder.
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Thermal decomposition reactions are endothermic because they absorb energy when the chemicals are heated.