ATOMIC STRUCTURE [dchemlc]

which of the following is not a subatomic particle?

• nucleus

• proton

• neutron

• electron

Answer explanation

Atoms are made of protons, neutrons and electrons. These particles are sometimes called sub-atomic particles because they are smaller than an atom.

how many protons are there in lead?

• 82

• 207

• 125

• 164

Answer explanation

The number of protons in an atom's nucleus is called its atomic number or proton number.

atomic number = number of protons

how many neutrons are there in Radon?

• 136

• 86

• 222

• 156

Answer explanation

The mass number counts the total number of protons and neutrons in the nucleus of the atom:

mass number = number of protons + number of neutrons

therefore;

number of neutrons = mass number - atomic number

Chlorine has two isotopes, chlorine-35 and chlorine-37. what are their atomic numbers respectively?

• 17 and 17

• 17 and 19

• 35 and 37

• 17 and 35

Answer explanation

Isotopes are atoms (of the same element) which have the same atomic number but different mass numbers. They have the same number of protons but different numbers of neutrons.

how many electrons are there in copper?

• 29

• 63

• 34

• 92

Answer explanation

Atoms are electrically neutral (they have no overall charge). The charge on a proton (+1) is equal but opposite to the charge on an electron (- 1), and therefore in an atom:

number of electrons =

number of protons

what is the electrical charge of an atom?

• 0

• 1

• -1

• 2

Answer explanation

Atoms are electrically neutral (they have no overall charge). The charge on a proton (+1) is equal but opposite to the charge on an electron (-1)

Chlorine consists of two isotopes, 35CI and 37CI, and a naturally occurring sample contains a mixture of these. Which isotope can be found in more abundance than the other?

• 35Cl isotope

• 37Cl isotope

• neither of these

Answer explanation

we can see that a naturally occurring sample of chlorine must contain more of the 35CI isotope than the 37CI isotope. This is because the relative atomic mass is closer to 35 than to 37.

an atom has 27 electrons and 32 neutrons. What is its mass number?

• 59

• 27

• 32

• 86

Answer explanation

The mass number (sometimes known as the nucleon number) counts the total number of protons and neutrons in the nucleus of the atom:

mass number = number of protons + number of neutrons

which of the following is not a molecule?

• magnesium

• oxygen gas

• water

• hydrogen gas

Answer explanation

A molecule consists of two or more atoms chemically bonded

what is the relative mass of an electron?

• 1/1836

• 1

• -1

• 0

Answer explanation