chemistry exam revision

remember by mondaym :)

difference between anion and cation

anion is an ion with a negative charge and a cation is an ion with a positive charge

what is a valance electron

the electrons on the outer shell

what substances form ionic bonds

metals and non metals

how is an ionic bond formed

when an atom loses an electron is becomes a positive ion (cation) and when an atom loses an electron it becomes a anion which both attract each other

2 examples of ionic compounds

sodium chloride NaCl and Magnesium oxide MgO

why do ionic substances have high melting points

because they are made up of positive and negative ions held together by ionic bonds, lots of heat is needed to break these bonds.

Explain why ionic bonds are brittle

when force is applied layers of positive and negative ions shift

explain why ionic substances conduct an electric current in the solution or molten

because ions can move freely allowing them to carry an electric current

what substances form covalent bonds

non-metals form covalent bonds

how is a covalent bond formed

by sharing other electrons

2 examples of covalent compounds

Water H2o Carbon dioxide CO2 Methane CH4

explain wy covalent substances have low melting points

they’re held together by small molecules held together by weak forces

define electronegativity

electronegativity is how much an atom wants to grab or pull electrons in a bond with another atom.