8.5A Atomic Structure STAAR Released

Which of these best describes one of the subatomic particles that could be found at location X in the model of an atom shown in the illustration.

• It has mass but no charge

• It has no mass and a positive charge

• It has a large mass and a negative charge

• It has no mass and an equal number of positive and negative charges

Answer explanation

The nucleus of the atom contains protons (positive charges) and neutrons (neutral/no charges).

Tags

NGSS.MS-PS1-1

Which of the following best describes an electron?

• It has no charge and about the same mass as a proton.

• It has a negative charge and much less mass than a proton.

• It has a positive charge and much more mass than a neutron.

• It has a negative charge and about the same mass as a neutron.

Answer explanation

Electrons are negatively charged subatomic particles with much less mass than a proton or a neutron.

An atom has 25 protons, 30 neutrons, and 25 electrons. What is the charge of the atom's nucleus?

• +25

• +30

• -25

• -30

Answer explanation

The charge of the nucleus is positive and equal to the number of protons.

Tags

NGSS.MS-PS1-1

A model of a beryllium atom is shown in the illustration. What type of particles are found in the cloud surroounding the atom's nucleus?

• Positively charged particles and negatively charged particles

• Negatively charged particles only

• Neutral particles and postiviely charged particles

• Positively charged particles only

Answer explanation

The electron cloud, containing negatively charged electrons, surrounds the nucleus of the atom

Tags

NGSS.MS-PS1-1

What is the mass number of a potassium (K) atom that has 20 neutrons?

• 18

• 19

• 20

• 39

Answer explanation

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

Tags

NGSS.MS-PS1-1

An atom of a certain element has 36 protons and 36 electrons and a mass number of 84. At room temperature this element is a very stable gas. How many neutrons are in this atom?

• 36

• 84

• 48

• 72

Answer explanation

the number is neutrons is equal to the mass number minus the number of protons. (84-36 =)

Tags

NGSS.MS-PS1-1

Ernest Rutherford's led to the understanding that an atom consists mostly of empty space with __________.

• protons orbiting a dense nucleus made of electrons and neutrons

• electrons orbiting a dense nucles made of protons and neutrons

• neutrons and protons orbiting a cloud electrons.

• electrons and protons orbiting a cloud of neutrons

Tags

NGSS.MS-PS1-1

What is the difference between the number of electrons in an atom of selenium (Se) and the number of electrons in an atom of aluminum (Al)?

• 34

• 47

• 21

• 13

Answer explanation

Atomic number of (Se) minus the atomic number of (Al)

Tags

NGSS.MS-PS1-1

How many protons, neutrons, and electrons are present in an atom of Hafnium (Hf) with a mass number of 178?

• 72 protons, 178 neutrons, 106 electrons

• 72 protons, 106 neutrons, 72 electrons

• 178 protons, 250 neutrons, 72 electrons

• 106 protons, 72 neutrons, 106 electrons

Answer explanation

The atomic number equals the number of protons in the nucles of the atom. The number of electrons equals the number of protons.

Tags

NGSS.MS-PS1-1

Which statement correctly describes the location and charge of the electrons in an atom?

• The electrons are inside the nucleus and have no charge.

• The electrons are outside the nucleus and have no charge

• The electrons are inside the nucleus and have a negative charge.

• The electrons are outside the nucleus and have a negative charge.

Answer explanation

The electrons are found in the energy levels of the electron cloud surrounding the nucleus.

Tags

NGSS.MS-PS1-1