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C1 Atomic structure and bonding (Ionic bonding (Ionic bonding occurs…
C1 Atomic structure and bonding
Structure of an atom
Neutrons are neutral, but protons and electrons are electrically charged. Protons have a relative charge of +1, while electrons have a relative charge of -1.
Electrons are arranged in energy levels or shells, and different energy levels can hold different numbers of electrons. The electronic structure of an atom is a description of how the electrons are arranged, which can be shown in a diagram or by numbers. There is a link between the position of an element in the periodic table and its electronic structure.
The total number of electrons in an atom is always the same as the number of protons in the nucleus. This means atoms have no overall electrical charge.
Atoms consist of electrons surrounding a nucleus that contains protons and neutrons.
At the centre of an atom is a nucleus containing protons and neutrons. Electrons are arranged around the nucleus in energy levels or shells.
Both protons and electrons have an electrical charge. Both have the same size of electrical charge, but the proton is positive and the electron negative. The neutron is neutral.
The number of protons in an atom is called its atomic number. In the periodic table atoms are arranged in atomic number order.
The total number of electrons in an atom is always the same as the number of protons in the nucleus. This means atoms have no overall electrical charge.
The number of protons in an atom is called its atomic number - also called the proton number. Atoms are arranged in the periodic table in order of increasing atomic number.
Covalent bonding
A covalent bond is formed between non metal atoms, which combine together by sharing electrons.
Covalent compounds have no free electrons and no ions so they don't conduct electricity.
Non metals combine together by sharing electrons. The shared pair of electrons holds the two atoms together. It's called a covalent bond. The group of atoms bonded together in this way is called a molecule.
The covalent bonds binding the atoms together are very strong but there are only very weak forces holding the molecules to each other (the intermolecular forces). Therefore, only a low temperature is needed to separate the molecules when they're melted or boiled.
The Periodic Table is an arrangement of the elements in order of atomic number. Elements in the same vertical column are in the same group or family and have similar chemical properties.
Ionic bonding
Ionic bonding occurs between positive and negative ions, which attract each other and bind together to form ionic compounds.
Each ion is surrounded by oppositely charged ions held in place by electrostatic attraction and forming an ionic crystal lattice. The ions in a crystal lattice are very strongly bonded - a high temperature is required to melt the crystal.
There are several ways in which atoms chemically combine together to make compounds. One of these ways is called ionic bonding. Atoms turn into ions when they lose or gain electrons.
Metal ions
In some circumstances metal atoms may lose electrons. The atom then has more protons than electrons and so it will be positively charged, a positive ion.
Example: A magnesium atom may lose two electrons and become a Mg2+ ion.
Non-metal ions
Non-metal atoms may gain electrons and become negatively charged.
Example: An oxygen atom may gain two electrons and become an O2- ion.
Ionic bonding
Positive and negative ions attract one another and bind together forming a new substance. This is called ionic bonding.
For example:
Sodium chloride consists of Na+ ions and Cl- ions bound together.
Magnesium oxide consists of Mg2+ ions and O2- ions bound together.
Ionic compounds like magnesium oxide and sodium chloride have high melting points and do not conduct electricity when solid. They do conduct electricity when molten. Sodium chloride is soluble in water and the solution conducts electricity.
Metallic bonding
High melting and boiling points
Metallic bonds are strong and a lot of energy is needed to break them. This is why metals have high melting points and boiling points.
The attraction between the metal ions and the delocalised electrons must be overcome to melt or to boil a metal. Some of the attractions must be overcome to melt a metal and all of them must be overcome to boil it. These attractive forces are strong, so metals have high melting and boiling points.
The delocalised electrons are able to move through the metal structure. When a potential difference is applied, they will move together, allowing an electric current to flow through the metal.
Conducting electricity
Metals contain electrons that are free to move in the metal structure, carrying charge from place to place and allowing metals to conduct electricity well.
The particles in a metal are held together by metallic bonds.
Metallic bonding
Metallic bonding is the strong attraction between closely packed positive metal ions and a 'sea' of delocalised electrons.