Question

1. atoms and chemicals

(a) explain the structure of an atom.

1. (a) sodium chloride is the most abundant salt in sea water.

(i) fig 2.1 shows the subatomic particles in an atom of sodium.
table 2.1 shows information about the structure of a sodium atom.
subatomic particle charge number present in a sodium atom
electron
neutron
proton +1
use fig. 2.1 to complete table 2.1
(ii) state the particle formed from an atom when electrons are lost or gained.
(b) calcium carbonate is found in animals.
(i) state the chemical formula of calcium carbonate.

Explanation:

Step1: Recall atomic structure knowledge

An atom has a nucleus with protons and neutrons, and electrons orbit the nucleus. For sodium (Na), atomic number is 11. Proton number = atomic number, so number of protons is 11.

Step2: Determine electron number

In a neutral atom, number of electrons = number of protons. So number of electrons in sodium is 11.

Step3: Identify particle formed by electron - gain/loss

When electrons are lost or gained, an ion is formed.

Step4: Recall chemical formula of calcium carbonate

Calcium has a + 2 charge ($Ca^{2+}$), carbonate is $CO_{3}^{2 - }$. The chemical formula of calcium carbonate is $CaCO_{3}$

Answer:

Subatomic particle	Charge	Number present in a sodium atom
Neutron	0	12
Proton	+ 1	11

(ii) Ion
(b)(i) $CaCO_{3}$