The atom is the basic unit of matter which goes into in a chemical reaction

a. Substances react together producing new substances. The activity which changes the substance into a new material is called chemical reaction.

b. An atom is the unit of the substance which undergoes a chemical reaction.

c. An atom that has less than 8 electrons in the last energy level is active.

It reacts with atoms of other elements to complete the last energy level with 8 electrons.
An example:
sodium atoms are active because each has an electron in the last energy level. In a chemical reaction sodium gives this electrons to atoms of another element & end up with 8 electrons in the last energy level.

d. Inert gases such as Argon ₁₈Ar has 8 electrons in the last energy level. They are stable & don’t react with other substances.

I. Fill in the blanks:

Name	Symbol	No. of protons	No. of neutrons	Electronic configuration
Hydrogen

II. Give reasons:

1. The atom is electrically neutral.

………………………………………………………………………………………………………………………………………………………………………………………………………….

2. The mass number is greater than the atomic number.

…………………………………………………………………………………………………………………………………………………………………………………………………………

3. The 3^rd energy level in the atom contains 18 electrons.

………………………………………………………………………………………………………………………………………………………………………………………………………….

4. The equation 2n² isn’t applied to the 4^th energy level.

………………………………………………………………………………………………………………………………………………………………………………………………………….

5. ₁₀Ne doesn’t go into chemical reactions.

……………………………………………………………………………………………………………………………………………………………………………………………………….

6. The mass of the atom is concentrated in the nucleus.

………………………………………………………………………………………………………………………………………………………………………………………………………….

III. Write the scientific term:

IV. Choose the right answer:

1. The second energy level in ₇N contains………….electrons.

(2 – 3 – 5)

2. The chemical activity of the element depends on the number of …………………….

(electrons in the outer level – protons – neutrons )

3. All the following elements are chemically active except…………………

(₁H – ₆C – ₁₈Ar)

V. Figure………………………is an excited atom while, figure…………………is for the atom in the ground state.

Figure A Figure B

Date: 2015-12-24; view: 786