FORMULA OF IONS

1. Ionic compounds made up of positive ions and negative ions.
2. To write the formula of an ionic compound, we need to know the symbol and charge of the ions in the compound.
3. Periodic table are divided by group 1-18.
4. group 1-3 are likely to donate their electron so they will become +ions, while other group such as group 16-17 are more likely to receive electron so that they become -ions.
5. for example; sodium, Na is group 1 and when it react with other element from group 17 (eg. chloride, Cl), Na will become +ve ions because it donate 1 electron to achieve it stability and Cl will become -ve ions because it will receive the electron from Na and became stabil molecule.

here are example of formula of ions that we need to know:

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RELATIVE MOLECULAR MASS

The relative molecular mass (Mr) of an element is the average mass of one molecule of the element/compound when compared with   of the mass of an atom of carbon-12, which taken as 12 units.

The relative molecular mass of a molecule is equal to the sum of the relative atomic mass of all the atoms in the molecule.

Example
Find the relative molecular mass of carbon dioxide.
[ JAR: C = 12; O = 16 ]

Answer:

The formula of carbon dioxide = CO2

Relative molecular mass of CO2 = 1 x 12 + 2 x 16 = 44

RELATIVE ATOMIC MASS

RELATIVE ATOMIC MASS , R.A.M

Relative mass

- is the relative mass of an object is the comparison of the mass of the object to the mass of a standard object.

Relative atomic mass , r.a.m

- is the relative atomic mass (Ar) of an element is the average mass of one atom of the element (Eg. Argon) when compared with 1/12 of the mass of an atom of carbon-12, which taken as 12 units.

Relative Atomic Mass

1. The mass of an atom when compared to another is known as the relative atomic mass (Ar).
2. The relative atomic mass (Ar) of an element is the average mass of one atom of the element when compared with  1/12 of the mass of an atom of carbon-12, which taken as 12 units.
3. 1/12 of the mass of an atom of carbon-12 is named as 1 atomic mass unit (amu).
4. The mass of one carbon atom is 12 amu.
5. 1/12 of the mass of an atom of carbon-12 is named as 1 atomic mass unit (amu).
6. The mass of one carbon atom is 12 amu.

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