Atomic Number and Mass Number

Q. A compound of carbon, hydrogen and nitrogen contains these elements in the ratio of 9:1:3.5. If the molecular mass of the compound is 108 g, then identify its correct molecular formula from the options given below.

1. $C_6{H}_8{N}_2$
2. $C_3{H}_{4}N$
3. $C_2{\mathrm{HN}}_2$
4. $C_2{H}_{2}N$

Q. Molecular mass of a nitrogen molecule is 28 u.

1. False
2. True

Q. Define the following terms:
“Cation and anion”

Q.

Mass number of an atom is represented by the letter M

1. True
2. False

Q. The percentage by mass of nitrogen atom in a molecule of ammonia is _____.

1. 18%
2. 25%
3. 52.65%
4. 82.35%

Q. What should be the neutron / proton ratio in the nucleus of a heavy element to be radioactive?
[1 Mark]

Q.

Give the electronic distribution in Magnesium atom and Magnesium ion. How do these electronic configurations differ?

Q. The mass of 1 mole of atom of an element is called its molar mass.

1. True
2. False

Q. How many electrons, neutrons and protons would be found in an atom of carbon -14 (atomic number 6)?

1. 6 electrons, 6 neutrons, 8 protons
2. 6 electrons, 6 neutrons, 6 protons
3. 8 electrons, 8 neutrons, 6 protons
4. 6 electrons, 8 neutrons, 6 protons

Q.

The mass of an atom is determined by the sum of the masses of

1. Electrons

2. Neutrons

3. Neutrons and protons

4. Electrons and neutrons

Q. The position of three elements $A$, $B$ and $C$ in the Periodic Table are shown below –

Group 16	Group 17
-	-
-	A
-	-
B	C

d) Which type of ion, cation or anion, will be formed by element $A$?

Q. Calculate the approximate temperature of 27${}^{\circ }C$ in Kelvin.

1. -273 K
2. -300 K
3. 273 K
4. 300 K

Q. Identify the element whose outermost orbit is partially filled with electrons in s and p subshells.

1. an inert gas
2. a representative element
3. a transition element
4. an inner transition element

Q.

What is a mass number?

Q.

Atomic mass = ______

1. Number of protons + Number of neutrons

2. Number of electrons + Number of neutrons

3. Number of electrons + Number of protons

4. Atomic number + Number of neutrons

Q.

Define the term mass number.

Q. Who discovered radioactivity? Who gave the name radioactivity?
[1 Mark]

Q. Define: Atomicity

Q.

Define “ Mass number”.

Q. Element 'X' reacts with chlorine to form a chloride compound of formula ${\text{XCl}}_4$. 'X' would most likely belong to the same group in the periodic table as that of:

1. Sodium
2. Silicon
3. Aluminium
4. Magnesium

Q. Maximum number of electrons that can occupy s, p, d and f sub shells respectively are:

1. 4, 5, 6, 7
2. 2, 6, 10, 14
3. 2, 4, 8, 16
4. 1, 2, 3, 4

Q. The percentage by mass of nitrogen atom in a molecule of ammonia is _____.

1. 18%
2. 25%
3. 52.65%
4. 82.35%

Q. How many moles of electrons are required to reduce 103.6 g of lead from $P{b}^{2+}$ to the metal?

1. 0.5 mole
2. 1 mole
3. 2 moles
4. 4 moles
5. 8 moles

Q. The diagram given below represents the atom of an element.
Which symbol gives the above information?

1. ${}_4^{9}Be$
2. ${}_4^{9}O$
3. ${}_4^{9}F$
4. ${}_4^{9}B$