Science M.C.Q-[Che-1M]

3. Thomson

2. Atomic number

2. All atoms have same number of protons and electrons

Explanation:

Atoms are smallest particle of an element.

They consists of solid mass in the center known as the nucleus in which protons and neutrons are present.

Outside the nucleus, there are present electrons which keep up on revolving around it.

Thus the atom is not mostly the empty space.

2. Neils Bohar

4. Cobalt-60

4. 2, 8, 1.

1. Chlorine

2. The electrons revolve around the nucleus in circular paths

Explanation:

The electrons revolve around the nucleus in circular paths was first proposed by Rutherford, not by Thomson.

1. Nucleus of atom contains only nucleons (neutrons and protons) was proposed by Rutherford.

Explanation:

Thomson proposed that the nucleus of an atom contains only nucleons.

1. It considered the nucleus is positively charged.

4. Helium nuclei, which impinged on a metal foil and got scattered

Explanation:

According to Rutherford's experiment, α− particles or helium nuclei impinged on a metal foil and got scattered.

3. An atom can have only electron and proton but o neutron.

Explanation:

An atom must have a proton and an electron, but it may not have a neutron.

For example: In hydrogen atom, there is 1 proton, 1 electron but no neutron.

1. An atom has equal number of electrons and protons.

Explanation:

When an atom has an equal number of electrons and protons, it has an equal number of negative electric charges (the electrons) and positive electric charges (the protons). The total electric charge of the atom is therefore zero and the atom is said to be neutral.

1. 2, 8

Explanation:

Magnesium ion, Mg²⁺ has 10 electrons; so, its electronic configuration is 2, 8.

4. The positively charged parts of an atom move with extremely high velocities

Explanation:

The conclusions of Rutherford's alpha scattering experiment do not include that the positively charged particles move with great velocities.

The positively charged particles are present at the center of the atom called a nucleus.

2. Circular

Explanation:

Rutherford proposed that the electrons revolve around the nucleus in circular paths.

The electrostatic force of attraction between the nucleus and electron provides centripetal force (force towards the centre).

1. 2, 8, 1

Explanation:

2, 8, 1 is the correct electronic configuration as the first shell can accommodate 2 electrons and second shell can accommodate 8 electrons. When the inner shell is full, electrons are filled in the outer shell.

3. Electrons revolve in a specific path around the nucleus

Explanation:

According to Rutherford's theory, electrons revolve in a specific path around the nucleus. An atom has no net charge or they are electrically neutral because electrons are negatively charged and the densely concentrated nucleus is positively charged.

2. An atom is a positively charged sphere with electrons embedded in it.

Explanation:

Thomson's model of atom states that:

An atom consists of a positively charged sphere with electrons embedded in it.

Total positive and negative charges in the atom are equal in magnitude. So, atom is electrically neutral.

1. Some of the α-particles rebound after hitting the gold foil.

3. Carbon

3. Carbon.

Explanation:

Carbon has 4 electrons in its outermost orbit. It completes its octet by sharing 4 electrons.

2. Isotopes are the atoms of different elements.

2. 2, 8, 2.

Explanation:

Explanation: Atomic number and the number of electrons in magnesium atom is 12.

So, electronic configuration is 2, 8, 2 (because 12 = 2 + 8 + 2).

3. Aluminium

Explanation:

Aluminium with three valence electrons has a valency = 3

Fluorine has seven valence electrons and has a valency = 1

Magnesium has two valence electrons and has a valency = 2

Carbon has four valence electrons and has a valency = 4

3. Magnesium

2. Ar, Ca are isobars and D, T, P are isotopes.

Explanation:

Isotopes - Protium, Tritium and Deuterium are isotopes of hydrogen.

Isobars - Argon and calcium; both have mass equal to 40.

Since isotopes have identical electronic configuration containing same number of valence electrons, they have similar chemical properties, but because the masses are slightly different hence, the physical properties (density, melting pt., boiling pt, etc) are different.

4. All of the above

Explanation:

Rutherford put forward the nuclear model of an atom, which had the following features:

There is a positively charged center in an atom called the nucleus.

The electrons revolve around the nucleus in circular paths.

The size of the nucleus is very small as compared to the size of the atom.

1. Uranium 235

1. An atom has equal number of protons and electrons.

Explanation:

An atom always has equal number of protons and electrons in order to maintain electrical neutrality.

3. Most part of the atom is empty space

4. unoccupied space

Explanation:

When alpha particles were bombarded on a gold foil, most of the alpha particles passed through undeflected.

This result indicates that most of the volume of a gold atom consists of unoccupied space.

This experiment is called the Rutherford experiment.

3. Helium nucleus.

2. Valency of an element.

2. Movement of electrons in discrete energy levels.

2. Mass number

4. The number of protons and neutrons.

4. 40

4. 35

3. (2, 6)

Explanation:

The total number of electrons present in oxygen is 8.

Therefore, for O electron configuration will be 1s²2s²2p⁴.

The distribution of electrons in oxygen atom is given by:

First orbit or K shell = 2(2n² = 2 × 1¹ = 2)

Second orbit or L shell = 6(8 − 2 = 6)

1. Positive

1. Atomic Number

1. 2 electrons

Explanation:

The valency shell means the outermost shell or orbit of an element which has valence electrons or outer electrons in it.

The atomic number of calcium is 20 and its electronic configuration is 2, 8, 8, 2 which shows that the outermost orbit or valency shell contains 2 electrons.

1. Na⁺, O^2-, Ne

Explanation:

Isoelectronic Species are those atoms which have the same electronic configuration or same number of electrons. For eg- N^3-, O^2-, F^-, Ne, Na⁺, Mg²⁺, Al³⁺ are a series of isoelectronic species.

4. 3

1. J.J. Thomson

Explanation:

J.J. Thompson discovered electrons by conducting a cathode-ray experiment.

4. empty

Explanation:

Hydrogen atom contains one proton in the nucleus and one electron outside the nucleus.

The space between a proton and electron in hydrogen atom is empty.

4. None of these

3. They have the same number of protons.

Explanation:

As the mass numbers are different, the correct option is (c). They have the same number of protons.