Why do atoms bond?
Noble gases such as helium, neon and argon are monoatomic because their valence shells are fully occupied by electrons. Thus, noble gases are stable and do not need to undergo bonding with other atoms.
Since only atoms with electronic configurations of noble gases are stable, then atoms bond to achieve the electronic configuration of a noble gas; or a fully filled valence shell. Atoms do so by transfer or sharing or electrons with other atoms.
By having an electronic configuration of a noble gas, an atom will achieve stability.
- When you have 2 electrons in the 1st shell, you have a duplet structure.
- When you have 8 electrons in the rest of the shells, you have an octet structure.
Chemical Bonds
There are 3 ways of forming chemical bonds between atoms:
- Ionic Bonding
- Covalent Bonding
- Metallic Bonding
1. Ionic Bonding
Ionic bonding is usually formed between metals and non-metals. These ionic bonds result from the transfer of electrons from metal atoms to non-metal atoms forming positive and negative ions (cations and anions). The electrical forces between these oppositely charged ions form strong ionic bonds.
Naming of ionic bonds:
[Name of cation][Name of anion]
e.g. Sodium Chloride
2. Covalent Bonding
Some atoms form bonds by sharing electrons to gain the electronic configuration of a noble gas (obtain a full valence shell). These bonds are known as covalent bonds.
A covalent bond is formed by the sharing of a pair of electrons between two atoms. Each atom contributes one electron to the bond. A covalent bond may have a single, double or triple covalent bond.
Generally, covalent bonds are formed between atoms of non-metal. Covalent bonds can be formed between atoms of same elements (O2, H2) or atoms of different elements (H2O, CO2). Compounds which contain covalent bonds are known as covalent compounds.
Single covalent bond - One pair of shared electrons between two atoms
Double covalent bond - Two pairs of shared electrons between two atoms
Triple covalent bond - Three pairs of shared electrons between two atoms
2. Covalent Bonding
Some atoms form bonds by sharing electrons to gain the electronic configuration of a noble gas (obtain a full valence shell). These bonds are known as covalent bonds.
A covalent bond is formed by the sharing of a pair of electrons between two atoms. Each atom contributes one electron to the bond. A covalent bond may have a single, double or triple covalent bond.
Generally, covalent bonds are formed between atoms of non-metal. Covalent bonds can be formed between atoms of same elements (O2, H2) or atoms of different elements (H2O, CO2). Compounds which contain covalent bonds are known as covalent compounds.
Single covalent bond - One pair of shared electrons between two atoms
Double covalent bond - Two pairs of shared electrons between two atoms
Triple covalent bond - Three pairs of shared electrons between two atoms
Making and breaking chemical bonds
When a chemical reaction occurs, one substance changes to another. This means that bonds in the reactants must first be broken and then new bonds must be made in the products. Breaking bonds involves pulling atoms apart and this requires energy. However, making bonds helps to make atoms and this gives out energy. So, bonk breaking is endothermic and bond making is exothermic.
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