Chemistry
Five atoms are labelled A to E.
| Atoms | Mass no. | Atomic no. |
|---|---|---|
| A | 40 | 20 |
| B | 19 | 9 |
| C | 7 | 3 |
| D | 16 | 8 |
| E | 14 | 7 |
(a) Which one of these atoms:
(i) contains 7 protons
(ii) has electronic configuration 2, 7?
(b) Write down the formula of the compound formed between C and D.
(c) Predict :
(i) metals
(ii) non-metals.
Atomic Structure
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Answer
(a) (i) Atom E.
As its atomic number is given as 7, therefore it contains 7 protons.
(ii) Atom B.
As its atomic number is 9, hence it has 9 electrons, therefore, its electronic configuration is 2, 7.
(b) Atom C has electronic configuration : [2, 1]
Atom D has electronic configuration : [2, 6]
As D requires two electrons to complete its octet, hence, it combines with two atoms of C which donate their valence electrons to attain stable noble gas configuration and D accepts the two electrons and attains a stable state, hence the formula of the compound formed between C and D is C2D
(c) (i) Metals: A [2,8,8,2] and C [2,1]
Reason — As the elements A and C have 2 and 1 electrons respectively in the valence shells hence, they are metals.
(ii) Non-metals: B [2,7], D [2,6], E [2,5].
Reason — As the elements B,D and E have 7,6 and 5 electrons respectively in the valence shell, hence they are non-metals.
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