Q: The charge on a single electron is approximately:

-1.6 \times 10^{-19} C. The magnitude of the electron's charge is 1.6 × 10⁻¹⁹ C, determined by Millikan. 9.1 × 10⁻³¹ kg is its mass, not charge.

Q: The charge-to-mass ratio (e/mₑ) of the electron has a value of about:

1.76 \times 10^{11} C/kg. Thomson measured e/mₑ = 1.76 × 10¹¹ C/kg for the electron. (9.58 × 10⁷ C/kg is the value for the proton.)

Q: The charge present on a proton is:

+1.6 \times 10^{-19} C. The proton carries a positive charge equal in magnitude to the electron's charge: +1.6 × 10⁻¹⁹ C.

Question 1

The electron was discovered by:

Accepted Answer

J. J. Thomson. J. J. Thomson (1897) studied cathode rays and established the existence of the electron, also measuring its charge-to-mass ratio.

Question 2

Cathode rays are a stream of:

Accepted Answer

Negatively charged particles (electrons). Cathode rays consist of electrons — negatively charged particles that travel from the cathode to the anode in a discharge tube.

Question 3

The charge on a single electron is approximately:

Accepted Answer

-1.6 	imes 10^{-19} C. The magnitude of the electron's charge is 1.6 × 10⁻¹⁹ C, determined by Millikan. 9.1 × 10⁻³¹ kg is its mass, not charge.

Question 4

The charge-to-mass ratio (e/mₑ) of the electron has a value of about:

Accepted Answer

1.76 	imes 10^{11} C/kg. Thomson measured e/mₑ = 1.76 × 10¹¹ C/kg for the electron. (9.58 × 10⁷ C/kg is the value for the proton.)

Question 5

Millikan's oil drop experiment was designed to determine the:

Accepted Answer

Charge on the electron. Millikan's oil drop experiment measured the charge on the electron (1.6 × 10⁻¹⁹ C) and showed that charge is always an integral multiple of this value.

Question 6

The charge-to-mass ratio (e/m) of the electron was first determined by:

Accepted Answer

J. J. Thomson. Thomson determined e/m of the electron by studying the deflection of cathode rays in electric and magnetic fields.

Question 7

The neutron was discovered by:

Accepted Answer

James Chadwick. James Chadwick (1932) discovered the neutron by bombarding beryllium with α-particles, producing a neutral radiation.

Question 8

Anode rays (canal rays), which led to the discovery of the proton, were first observed by:

Accepted Answer

E. Goldstein. E. Goldstein (1886) discovered canal rays (anode rays) using a perforated cathode; the lightest positive particle (from hydrogen) was later identified as the proton.

Question 9

The charge present on a proton is:

Accepted Answer

+1.6 	imes 10^{-19} C. The proton carries a positive charge equal in magnitude to the electron's charge: +1.6 × 10⁻¹⁹ C.

Question 10

In an electric field, cathode rays are deflected towards the:

Accepted Answer

Positive plate. Being negatively charged, cathode ray electrons are attracted to and deflected towards the positive plate.

Question 11

The particle that has a mass of about 1 atomic mass unit and a charge of +1 is the:

Accepted Answer

Proton. The proton has mass ≈ 1 u and charge +1. The neutron also has mass ≈ 1 u but is neutral; the electron is far lighter.

Question 12

The discovery of the proton is associated with the study of:

Accepted Answer

Anode rays (canal rays). Positive (anode/canal) rays, produced from a perforated cathode, led to the identification of the proton as the lightest positive particle (from hydrogen).

Question 13

Which statement about the neutron is correct?

Accepted Answer

It is electrically neutral with mass close to that of a proton. The neutron is neutral, has a mass just above the proton's, and was discovered (1932) long after the electron (1897).

Question 14

Thomson's model of the atom is popularly known as the:

Accepted Answer

Plum pudding model. Thomson pictured the atom as a sphere of positive charge with electrons embedded in it, like plums in a pudding (also called the watermelon model).

Question 15

In Thomson's model, the electrons are:

Accepted Answer

Embedded in a sphere of uniform positive charge. Thomson proposed a uniform sphere of positive charge with the negatively charged electrons studded throughout it, keeping the atom neutral.

Question 16

In Rutherford's α-particle scattering experiment, the metal foil used was made of:

Accepted Answer

Gold. Rutherford (with Geiger and Marsden) bombarded a very thin gold foil with α-particles.

Question 17

In the α-scattering experiment, the observation that most α-particles passed straight through the foil showed that:

Accepted Answer

The atom is mostly empty space. Since the vast majority of α-particles went through undeflected, most of the atom's volume must be empty space.

Question 18

The atomic number (Z) of an element is equal to the number of:

Accepted Answer

Protons in the nucleus. The atomic number Z is the number of protons in the nucleus (equal to the number of electrons in a neutral atom).

Question 19

The mass number (A) of an atom is given by:

Accepted Answer

Number of protons + number of neutrons. Mass number A = number of protons (Z) + number of neutrons (N). Neutrons = A − Z.

Question 20

Isotopes of an element have the same:

Accepted Answer

Atomic number but different mass number. Isotopes have the same number of protons (same Z) but different numbers of neutrons, so different mass numbers.

Atomic Structure — NEET Chemistry MCQs with Solutions

Subtopics

Sample questions with solutions