U2L2 DE EQ

Which subatomic particle has the smallest mass?

• Proton

• Neutron

• Electron

• All have equal mass

Answer explanation

The electron has the smallest mass among subatomic particles, significantly lighter than protons and neutrons. Protons and neutrons have similar masses, but both are much heavier than electrons.

The charge on a proton is ____, the charge on an electron is ____, and the charge on a neutron is ____.

• +1, -1, 0

• -1, +1, 0

• 0, +1, -1

• +1, 0, -1

Answer explanation

The charge on a proton is +1, indicating a positive charge. The charge on an electron is -1, indicating a negative charge. A neutron has no charge, represented as 0. Therefore, the correct answer is +1, -1, 0.

What holds the nucleus together despite the repulsion between protons?

• Electromagnetic force

• Gravitational force

• Strong nuclear force

• Weak nuclear force

Answer explanation

The strong nuclear force is the fundamental force that holds the nucleus together, overcoming the electromagnetic repulsion between protons. It acts between nucleons (protons and neutrons) at very short ranges.

Tags

NGSS.HS-PS1-8

Atoms with the same atomic number but different mass numbers are called:

• Ions

• Isotopes

• Molecules

• Compounds

Answer explanation

Atoms with the same atomic number have the same number of protons, while different mass numbers indicate varying numbers of neutrons. These variations are known as isotopes, making 'Isotopes' the correct answer.

The number of protons in an atom is called the:

• Mass number

• Atomic mass

• Atomic number

• Neutron number

Answer explanation

The atomic number of an atom is defined as the number of protons it contains. This is a fundamental property that determines the element's identity, making 'Atomic number' the correct answer.

Tags

NGSS.HS-PS1-7

An atom has a mass number of 23 and an atomic number of 11. How many neutrons does it have?

• 11

• 12

• 23

• 34

Answer explanation

To find the number of neutrons, subtract the atomic number from the mass number. Here, 23 (mass number) - 11 (atomic number) = 12 neutrons. Therefore, the correct answer is 12.

Tags

NGSS.MS-PS1-1

Which is the correct way to write the symbol for carbon-14?

• ¹⁴C

• 14C

• ⁶C¹⁴

• 6C14

Answer explanation

The correct way to write the symbol for carbon-14 is ¹⁴C, where the superscript 14 indicates the atomic mass. The other options do not follow the standard notation for isotopes.

Which pair represents isotopes of the same element?

• ¹²C and ¹³C

• ¹⁶O and ¹⁶S

• ²³Na and ²⁴Mg

• ¹H and ⁴He

Answer explanation

¹²C and ¹³C are isotopes of carbon, differing in neutron number (6 and 7 respectively) but having the same atomic number (6). The other pairs represent different elements or different atomic numbers.

How many electrons does an atom with atomic number 15 have?

• 15

• 30

• It depends on the mass number

• Cannot be determined

Answer explanation

An atom's atomic number indicates the number of protons, which equals the number of electrons in a neutral atom. Therefore, an atom with atomic number 15 has 15 electrons.

What is the mass number of an atom that has 17 protons and 18 neutrons?

• 17

• 18

• 35

• 1

Answer explanation

The mass number of an atom is the sum of its protons and neutrons. Here, there are 17 protons and 18 neutrons, so the mass number is 17 + 18 = 35. Therefore, the correct answer is 35.