Question 1

What is the atomic number of an atom that contains 9 protons,9 electrons,and 10 neutrons?
A)9
B)10
C)18
D)19

Accepted Answer

The atomic number of an atom is determined by the number of protons it contains, which in this case is 9.

Question 2

Which subatomic particle contributes least to the mass of the nucleus?
A)Proton
B)Neutron
C)Electron

Accepted Answer

Electrons do not contribute to the mass of the nucleus as they are found in the electron cloud outside the nucleus. Protons and neutrons contribute to the mass of the nucleus.

Question 3

The combined number of protons and neutrons in an atom is known as its
A)atomic number.
B)mass number.
C)atomic mass.
D)molecular mass.

Accepted Answer

The mass number is the sum of the number of protons and neutrons in an atom.

Question 4

An isotope of sodium has the atomic number 11 and the mass number 23.An atom of this isotope contains
A)12 electrons
B)12 protons
C)12 neutrons
D)23 electrons

Accepted Answer

Sodium has an atomic number of 11, meaning it has 11 protons and, in a neutral atom, 11 electrons. The mass number is 23, which is the sum of protons and neutrons. Therefore, it has 23 - 11 = 12 neutrons.

Question 5

One isotope of carbon has the atomic number 6 and the mass number 14.An atom of this isotope contains
A)8 protons
B)14 neutrons
C)6 neutrons
D)6 electrons

Accepted Answer

The atomic number of carbon (6) indicates it has 6 protons and, since it's neutral, also 6 electrons. The mass number (14) minus the atomic number (6) gives the number of neutrons, which is 8, not 6 or 14.

Question 6

Naturally occurring neon exists as three isotopes.90.51% is Ne-20 with a mass of 19.99 amu,0.27% is Ne-21 with a mass of 20.99 amu,and 9.22% is Ne-22 with a mass of 21.99 amu.What is the atomic mass of neon?
A)10.00 amu
B)20.18 amu
C)20.99 amu
D)62.97 amu

Accepted Answer

To find the atomic mass of neon, we need to take a weighted average of the masses of its isotopes. We can use the percent abundances as weights. 
Atomic mass of neon = (0.9051 x 19.99 amu) + (0.0027 x 20.99 amu) + (0.0092 x 21.99 amu) 
= 18.08849 + 0.056673 + 0.202708 
= 18.34787 amu ≈ 20.18 amu (rounded to two decimal places) 
Therefore, the correct option is B.

Question 7

Atoms of isotopes of an element contain the same number of
A)protons.
B)neutrons.
C)alpha particles.

Accepted Answer

Isotopes of an element have the same number of protons (which defines the element) but differ in the number of neutrons.

Question 8

The electrical charge of an atom is
A)positive.
B)negative.
C)the atom has no charge,it is neutral.

Accepted Answer

The electrical charge of an atom is neutral. This means that the atom has an equal number of positively charged protons and negatively charged electrons, making the overall charge of the atom zero.

Question 9

Atoms of isotopes of an element contain different numbers of
A)protons.
B)neutrons.
C)electrons.

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons, which is what makes them isotopes. The number of electrons stays the same because it is determined by the number of protons, which is the atomic number of the element.

Question 10

In isotopic notation atomic number is represented by the subscript
A)A
B)N
C)P
D)Z

Accepted Answer

In isotopic notation, the atomic number is represented by the subscript Z.

Question 11

One isotope of oxygen has the atomic number 8 and the mass number 18.An atom of this isotope contains
A)8 neutrons
B)10 electrons
C)8 protons
D)18 electrons

Accepted Answer

The atomic number (8) indicates the number of protons, which is 8 for oxygen, regardless of the isotope.

Question 12

Different isotopes of an element are atoms of that element which have
A)the same atomic number and the same mass number.
B)the same atomic number and different mass number.
C)different atomic number and the same mass number.
D)different atomic number and different mass number.

Accepted Answer

Isotopes are atoms of the same element with different numbers of neutrons, which means they have the same atomic number (since it is determined by the number of protons in the nucleus) but different mass numbers (since the mass number is determined by the total number of protons and neutrons in the nucleus). Therefore, option B (same atomic number but different mass number) is correct.

Question 13

Which particle contributes most to the electrical charge of the nucleus?
A)Proton
B)Neutron
C)Electron

Accepted Answer

Protons carry a positive charge, while neutrons carry no charge (they are neutral) and electrons carry a negative charge. Since the electrical charge of the nucleus (the center of an atom where protons and neutrons reside) is positive due to the presence of protons, it follows that protons contribute most to the electrical charge of the nucleus.

Question 14

In isotopic notation mass number is represented by the superscript
A)A
B)N
C)P
D)Z

Accepted Answer

In isotopic notation, the mass number of an atom is represented by the superscript "A." This refers to the total number of protons and neutrons in the nucleus of the atom.

Question 15

Which subatomic particle contributes least to the mass of an atom?
A)Proton
B)Neutron
C)Electron

Accepted Answer

Electrons contribute the least to the mass of an atom as they are much lighter than protons and neutrons. Protons and neutrons are located in the nucleus of an atom and make up the majority of its mass.

Question 16

Naturally occurring silicon exists as three isotopes.92.23% is Si-28 with a mass of 27.977 amu,4.67% is Si- 29 with a mass of 28.977 amu,and 3.10% is Si-30 with a mass of 29.974 amu.What is the atomic mass of silicon?
A)14.00 amu
B)28.09 amu
C)28.98 amu
D)86.93 amu

Accepted Answer

To calculate the atomic mass of silicon, we need to take into account the percent abundance and mass of each isotope.

Atomic mass = (% abundance of Si-28 × mass of Si-28) + (% abundance of Si-29 × mass of Si-29) + (% abundance of Si-30 × mass of Si-30)

Atomic mass = (0.9223 × 27.977 amu) + (0.0467 × 28.977 amu) + (0.0310 × 29.974 amu)

Atomic mass = 28.086 amu or approximately 28.09 amu. Thus, the best choice is B.

Question 17

Which subatomic particle is not found in the nucleus of the atom?
A)Proton
B)Neutron
C)Electron

Accepted Answer

Electrons are located outside the nucleus in the electron cloud. Protons and neutrons make up the nucleus.

Question 18

The mass of a copper atom is 1.045 x 10^-22g.How many copper atoms are present in a 94.5g sample of copper? A)9.04 x 10²³ B)1.045 x 10^-22 C)1870 D)94.5

Accepted Answer

First, we need to calculate the number of moles of copper in the 94.5g sample:
number of moles = mass / molar mass
The molar mass of copper can be calculated from the atomic mass of copper:
molar mass = atomic mass * Avogadro's constant
molar mass = 63.546 g/mol * 6.022 x 10^23 /mol
molar mass = 1.908 x 10^25 /mol
number of moles = 94.5g / 1.908 x 10^25 /mol
number of moles = 4.95 x 10^-23 mol
Now, we can calculate the number of copper atoms:
number of atoms = number of moles * Avogadro's constant
number of atoms = 4.95 x 10^-23 mol * 6.022 x 10^23 /mol
number of atoms = 2.98 x 10^1 /mol
number of atoms = 2.98 x 10^23
Therefore, the answer is A, 9.04 x 10^23.

Question 19

The number of protons in an atom is known as its
A)atomic Mass.
B)atomic number.
C)mass number.
D)molecular mass.

Accepted Answer

The atomic number of an element is defined as the number of protons present in the nucleus of an atom. It is a unique number for each element and determines the chemical properties of that element. It is usually represented by the symbol "Z".

Question 20

The electrical charge of a nucleus is
A)positive.
B)negative.
C)the nucleus has no charge,it is neutral.

Accepted Answer

The electrical charge of a nucleus is positive because it is composed of positively charged protons and uncharged neutrons. The number of protons in the nucleus determines its atomic number, which also determines the element to which it belongs.

Quiz 5: Early Atomic Theory and Structure

What is the atomic number of an atom that contains 9 protons,9 electrons,and 10 neutrons?

Which subatomic particle contributes least to the mass of the nucleus?

The combined number of protons and neutrons in an atom is known as its

An isotope of sodium has the atomic number 11 and the mass number 23.An atom of this isotope contains

One isotope of carbon has the atomic number 6 and the mass number 14.An atom of this isotope contains

Naturally occurring neon exists as three isotopes.90.51% is Ne-20 with a mass of 19.99 amu,0.27% is Ne-21 with a mass of 20.99 amu,and 9.22% is Ne-22 with a mass of 21.99 amu.What is the atomic mass of neon?

Atoms of isotopes of an element contain the same number of

The electrical charge of an atom is

Atoms of isotopes of an element contain different numbers of

In isotopic notation atomic number is represented by the subscript

One isotope of oxygen has the atomic number 8 and the mass number 18.An atom of this isotope contains

Different isotopes of an element are atoms of that element which have

Which particle contributes most to the electrical charge of the nucleus?

In isotopic notation mass number is represented by the superscript

Which subatomic particle contributes least to the mass of an atom?

Naturally occurring silicon exists as three isotopes.92.23% is Si-28 with a mass of 27.977 amu,4.67% is Si- 29 with a mass of 28.977 amu,and 3.10% is Si-30 with a mass of 29.974 amu.What is the atomic mass of silicon?

Which subatomic particle is not found in the nucleus of the atom?

The mass of a copper atom is 1.045 x 10 -22 g.How many copper atoms are present in a 94.5g sample of copper?

The number of protons in an atom is known as its

The electrical charge of a nucleus is

The mass of a copper atom is 1.045 x 10^-22g.How many copper atoms are present in a 94.5g sample of copper?