Ionic compounds Flashcards
Key concepts in chemistry
anion
Definition
An atom or group of atoms that have gained electrons and become negatively charged. Most anions are formed from non-metals.
aqueous
Definition
Dissolved in water to form a solution. Shown as (aq) in chemical equations.
atom
Definition
The smallest part of an element that can exist.
atomic number
Definition
The number of protons in the nucleus of an atom. Also called the proton number.
boiling point
Definition
The temperature at which a substance rapidly changes from a liquid to a gas.
cation
Definition
An atom or group of atoms that have lost electrons and become positively charged. Most cations are formed from metals.
charge
Definition
Property of matter that causes a force when near another charge. Charge comes in two forms, positive and negative. For example, a negative charge causes a repulsive force on a neighbouring negative charge.
charged particles
Definition
Particles, usually ions or electrons, that carry electrical charges.
compound
Definition
A substance formed by the chemical union of two or more elements.
conduct
Definition
To allow electricity, heat or other energy forms to pass through.
electron
Definition
Subatomic particle, with a negative charge and a negligible mass relative to protons and neutrons.
electrostatic force
Definition
A force of attraction between particles with opposite charges.
ionic bonding
Definition
Ionic bonding forms between two atoms when an electron is transferred from one atom to the other, forming a positive-negative ion pair.
ionic compound
Definition
An ionic compound occurs when a negative ion (an atom that has gained an electron) joins with a positive ion (an atom that has lost an electron).
ionic lattice
Definition
The regular arrangement of ions in an ionic substance.
molten
Definition
A term used to describe a liquid substance (eg rock, glass or metal) formed by heating a solid.
polyatomic ion
Definition
Charged particle consisting of two or more atoms joined together.
Which type of elements gain/lose atoms to form ions?
metal atoms lose electrons to form positively charged ions
non-metal atoms gain electrons to form negatively charged ions
Forming positive ions
Metal atoms lose electrons from their outer shell when they form ions:
- the ions formed are positive, with more protons than electrons
- the ions formed have full outer shells
Forming negative ions
The outer shell of non-metal atoms gains electrons when they form ions:
- the ions formed are negative, because they have more electrons than protons
- the ions formed have full outer shells
How can the number of protons, neutrons and electrons in an ion be calculated?
The numbers of protons, neutrons and electrons in an ion can be calculated from its atomic number, mass number and ionic charge.
Have positive ions gained or lost electrons?
Lost
Have negative ions gained or lost an electron?
Gained
Positively charged ions are called what?
cations
Negatively charged ions are called what?
anions
How are ions formed?
Ions can form when a metal reacts with a non-metal, by transferring electrons. The oppositely charged ions are strongly attracted to each other, forming ionic bonds.
How are ionic bonds formed?
Ions can form when a metal reacts with a non-metal, by transferring electrons. The oppositely charged ions are strongly attracted to each other, forming ionic bonds.
How are the ions in a solid ionic compound arranged?
The ions in a solid ionic compound are not randomly arranged. Instead, they have a regular, repeating arrangement called an ionic lattice. The lattice is formed because the ions attract each other and form a regular pattern with oppositely charged ions next to each other.
How are ionic lattices formed?
The ions in a solid ionic compound are not randomly arranged. Instead, they have a regular, repeating arrangement called an ionic lattice. The lattice is formed because the ions attract each other and form a regular pattern with oppositely charged ions next to each other.
giant. 3d.
How big is a ionic lattice?
Remember that the lattice arrangement is giant - for example, a single grain of salt may contain 1.2 × 1018 (1,200,000,000,000,000,000) ions. The lattice arrangement continues in three dimensions. This is why solid ionic compounds form crystals with regular shapes.
What are ionic bonds?
Ionic bonds are strong electrostatic forces between oppositely charged ions.
Ionic bonds
The ionic lattice is held together by ionic bonds. In three-dimensional models, ionic bonds are shown as straight lines between ions. This is to keep things simple because ionic bonds can act in any direction.
How is the ionic lattice held together?
The ionic lattice is held together by ionic bonds.
What direction(s) can ionic bonds act in?
Any
How are ionic bonds show in a 3d model?
In three-dimensional models, ionic bonds are shown as straight lines between ions. This is to keep things simple because ionic bonds can act in any direction.
What is the state of any ionic compound at room temperature?
Solid
Energy has to be transferred to a substance in order to melt or boil it. This energy is needed to break the bonds between particles in the substance:
- some bonds are overcome during melting
- all remaining bonds are overcome during boiling
How are ionic compounds held together?
Ionic compounds are held together by many strong electrostatic forces between the oppositely charged ions.
These forces are usually referred to as ionic bonds.
are bonds in an ionic lattice easy or hard to break?
As the ionic lattice contains such a large number of ions, a lot of energy is needed to overcome these ionic bonds so ionic compounds have high melting and boiling points.
A substance can conduct electricity if:
- it contains charged particles, and
- these particles are free to move from place to place
When are ionic compounds conductors of electricity?
basic
Ionic compounds are conductors of electricity when molten or in solution and insulators when solid.
When are ionic compounds conductors of electricity?
detailed
Ionic compounds conduct electricity when molten to form a liquid or dissolved in water to form an aqueous solution.
This is because both processes make their ions free to move from place to place. Ionic compounds cannot conduct electricity when solid, as their ions are held in fixed positions and cannot move.
How to work out the formula for an ionic compound
To deduce the formulae of ionic compounds, the formulae of their ions can be used.
The formula for an ionic compound must contain the same number of positive and negative charges so that the charges are balanced and it is neutral overall.
Working out the formula of an ionic compound
example
Sodium chloride contains Na+ and Cl- ions:
this is one positive charge and one negative charge
the charges are balanced
so the formula is NaCl
Working out the formula of an ionic compound
example
Magnesium oxide contains Mg^2+ and O^2- ions:
this is two positive charges and two negative charges
the charges are balanced
so the formula is MgO
Working out the formula of an ionic compound
example
Aluminium oxide contains Al^3+ and O^2- ions:
this is three positive charges and two negative charges
to balance, we need two Al^3+ ions and three O^2- ions
so the formula is Al(2)O(3)
How are the formulae of compounds containing polyatomic ions are worked out?
The formulae of compounds containing polyatomic ions are worked out in a similar way to single atom ions. Except when there is more than one polyatomic ion, then its formula is written inside brackets.
Working out the formula of a polyatomic ion
example
Calcium hydroxide contains Ca^2+ and OH- ions:
this is two positive charges and one negative charge
to balance it will need, one Ca^2+ ions and two OH- ions
so the formula is Ca(OH)(2)
Q. Deduce the formula for sodium carbonate.
Sodium carbonate contains Na+ and CO(3)^2- ions:
this is one positive charge and two negative charges
to balance, two Na+ ions and one CO(3)^2- ions are needed
so the formula is Na(2)CO^3
Q. Deduce the formula for lead nitrate.
Lead nitrate contains Pb^2+ and NO(3)- ions:
this is two positive charges and one negative charge
to balance it will need one Pb^2+ ion and two NO(3)- ions
so the formula is Pb(NO(3))(2)
The name of an ionic compound ends in:
- ide if it contains just two elements
- ate if it contains three or more elements, one of which is oxygen
