1.
The nucleus of an atom
Correct Answer
D. Usually contains protons and neutrons
Explanation
The nucleus of hydrogen atom contains only proton.
2.
Which of the following statements about the atom
is true?
Correct Answer
A. No of electrons= no of protons
Explanation
The statement "no of electrons = no of protons" is true. In an atom, the number of electrons is equal to the number of protons. This is because atoms are electrically neutral, meaning they have an equal number of positive protons and negative electrons. The number of neutrons, on the other hand, can vary in different atoms of the same element, resulting in different isotopes.
3.
The neutron is a particle that has
Correct Answer
C. A mass that is approximately that of the proton
Explanation
Neutrons are particles that have a mass that is approximately the same as that of protons. While the mass of a neutron is not exactly 1g, it is very close to the mass of a proton. Neutrons do not have a charge, unlike protons which have a positive charge, and electrons which have a negative charge. Therefore, the statement that the neutron has a mass that is approximately that of the proton is the correct answer.
4.
The nucleon number of chlorine is 35 and its
proton number is 17. It can therefore be deduced that the atom has
Correct Answer
B. 18 neutrons
Explanation
Since the nucleon number of an atom is the sum of its protons and neutrons, and the proton number is the number of protons, we can subtract the proton number from the nucleon number to find the number of neutrons. In this case, 35 (nucleon number) minus 17 (proton number) equals 18 neutrons.
5.
All isotopes of an element contain
Correct Answer
D. The same number of protons
Explanation
All isotopes of an element have the same number of protons because the number of protons determines the element's identity. Isotopes are variants of an element that have the same number of protons but different numbers of neutrons. The number of electrons in an atom is equal to the number of protons to maintain electrical neutrality. Therefore, the statement "the same number of protons" is the correct answer.
6.
The structures of five atoms are given in the
table below. Determine which pairs are isotopes.
Atom
No. of neutrons
No. of
electrons
No. of protons
P
16
15
15
Q
16
16
16
R
17
15
15
S
17
17
17
T
18
16
16
Correct Answer
A. P & R
Explanation
Isotopes are atoms of the same element that have different numbers of neutrons. In this case, atoms P and R have the same number of protons (15) and electrons (15), but different numbers of neutrons (P has 16 and R has 17). Therefore, P and R are isotopes.
7.
The chlorine atom and ion are
Correct Answer
D. Have the same number of protons
Explanation
The explanation for the given correct answer is that the chlorine atom and ion have the same number of protons. Protons are positively charged particles found in the nucleus of an atom, and they determine the atomic number and identity of an element. Since the chlorine atom and ion are chemically identical, it means they have the same number of protons. This is because an ion is formed when an atom gains or loses electrons, but the number of protons remains the same. Therefore, the chlorine atom and ion have the same number of protons.
8.
The atoms in the Periodic Table are arranged in
terms of
Correct Answer
A. Ascending proton numbers
Explanation
The atoms in the Periodic Table are arranged in terms of ascending proton numbers because the number of protons in an atom's nucleus determines its atomic number. The atomic number defines the element and its position in the Periodic Table. As we move from left to right across a period, the atomic number increases by one, indicating the addition of one proton to the nucleus. This arrangement allows for a systematic organization of elements based on their properties and helps in predicting the behavior of elements in chemical reactions.
9.
The sulphur atom contains 16 electrons. It can
be deduced that
Correct Answer
A. It has 16 valence electrons
Explanation
The explanation for the given correct answer is that the number of valence electrons in an atom is equal to the number of electrons in the outermost energy level. Since the sulphur atom contains 16 electrons, we can deduce that it has 16 valence electrons. The other statements in the question are not relevant to the number of valence electrons in the sulphur atom.
10.
Elements in the same group of the Periodic Table
have the
Correct Answer
B. Same number of valence electrons
Explanation
Elements in the same group of the Periodic Table have the same number of valence electrons. Valence electrons are the electrons in the outermost energy level of an atom. Elements in the same group have the same number of valence electrons because they have similar electron configurations. This similarity in valence electrons allows elements in the same group to have similar chemical properties and react in similar ways.
11.
Valence electrons refer to those that
Correct Answer
D. Exist in the outermost shell of the atom
Explanation
Valence electrons are the electrons that exist in the outermost shell of an atom. These electrons are involved in chemical bonding and determine the atom's reactivity and ability to form chemical bonds with other atoms.
12.
Which of the following represents the electronic
configuration of calcium (atomic number of Ca = 20)?
Correct Answer
B. (2, 8, 8, 2)
Explanation
The 1st shell can take in 2 electrons; the second shell can take in maximum of 8 electrons; the 3rd shell also can take in maximum of 8 electrons.