Match the atomic numbers 4, 8, 10, 15 and 19 with each of the following:
(a) Element which can form trivalent ions.
(b) An element with 4 shells.
(c) Element with 6 valence electrons.
(d) Element which does not form ions.
Match the atomic numbers 4, 8, 10, 15 and 19 with each of the following:
(a) Element which can form trivalent ions.
(b) An element with 4 shells.
(c) Element with 6 valence electrons.
(d) Element which does not form ions.
Electronic configuration: Electronic configuration is the arrangement of electrons in the various shells around the nucleus of an atom in the increasing order of energy.
- Electrons begin to fill from the innermost orbit to the outermost.
S. No Atomic number Electronic configuration Valence electrons Number of shells 1 4 2, 2 2 2 2 8 2, 6 6 2 3 10 2, 8 8 2 4 15 2, 8, 5 5 3 5 19 2, 8, 8, 1 1 4
(a) Element which can form trivalent ions- Atomic number 15
Trivalent ion is formed by the gain or loss of 3 electrons (Tri means three).
- Three electrons will be gained by an atom that has 5 electrons in its outermost shell so that it can complete its octet of electrons and gain stability. From the above table, element that has 5 valence electrons is atomic number 15.
(b) An element with 4 shells- Atomic number 19
Atomic number= 19 Number of electrons= 19. These 19 electrons are arranged in four shells.
- First shell- 2 electrons
- Second shell- 8 electrons
- Third shell- 8 electrons
- Fourth shell- 1 electron
(c) Element with 6 valence electrons- Atomic number 8
Valence shell is the outermost shell and the electrons present in this shell are called as valence electrons.
From the above table, atomic number 8 has 6 valence electrons.
(d) Element which does not form ions- Atomic number 10
Ions are formed by the elements which do not have a stable nearest noble gas configuration. Alternatively, the elements that do not have 8 (octet) or 2 (duplet) of electrons form ions by the gain or loss of electrons. As atomic number 10 already has 8 electrons in its outermost shell, therefore it will not form ions.
(a) Element which can form trivalent ions Atomic number 15 (b) Element which can form trivalent ions Atomic number 19 (c) Element with 6 valence electrons Atomic number 8 (d) Element which does not form ions Atomic number 10
Electronic configuration: Electronic configuration is the arrangement of electrons in the various shells around the nucleus of an atom in the increasing order of energy.
- Electrons begin to fill from the innermost orbit to the outermost.
| S. No | Atomic number | Electronic configuration | Valence electrons | Number of shells |
| 1 | 4 | 2, 2 | 2 | 2 |
| 2 | 8 | 2, 6 | 6 | 2 |
| 3 | 10 | 2, 8 | 8 | 2 |
| 4 | 15 | 2, 8, 5 | 5 | 3 |
| 5 | 19 | 2, 8, 8, 1 | 1 | 4 |
(a) Element which can form trivalent ions- Atomic number 15
Trivalent ion is formed by the gain or loss of 3 electrons (Tri means three).
- Three electrons will be gained by an atom that has 5 electrons in its outermost shell so that it can complete its octet of electrons and gain stability. From the above table, element that has 5 valence electrons is atomic number 15.
(b) An element with 4 shells- Atomic number 19
Atomic number= 19 Number of electrons= 19. These 19 electrons are arranged in four shells.
- First shell- 2 electrons
- Second shell- 8 electrons
- Third shell- 8 electrons
- Fourth shell- 1 electron
(c) Element with 6 valence electrons- Atomic number 8
Valence shell is the outermost shell and the electrons present in this shell are called as valence electrons.
From the above table, atomic number 8 has 6 valence electrons.
(d) Element which does not form ions- Atomic number 10
Ions are formed by the elements which do not have a stable nearest noble gas configuration. Alternatively, the elements that do not have 8 (octet) or 2 (duplet) of electrons form ions by the gain or loss of electrons. As atomic number 10 already has 8 electrons in its outermost shell, therefore it will not form ions.
| (a) | Element which can form trivalent ions | Atomic number 15 |
| (b) | Element which can form trivalent ions | Atomic number 19 |
| (c) | Element with 6 valence electrons | Atomic number 8 |
| (d) | Element which does not form ions | Atomic number 10 |
