7.PS1.1 Atomic Structure

Examine the drawing of a Bohr model of an atom with the nucleus and two orbitals. Where should the electrons be placed in the model?

• on the lines of the orbitals

• inside the nucleus

• in the space between the two orbitals

• in the space between the nucleus and the first orbital

Answer explanation

In a Bohr model, electrons are placed on the lines of the orbitals, representing their specific energy levels. This placement indicates the allowed paths for electrons around the nucleus, making 'on the lines of the orbitals' the correct choice.

Tags

NGSS.MS-PS1-1

A student makes a model of an atom, as shown. Where should the student place a proton in the model?

• inside the nucleus

• on either of the two orbits

• between the two orbits

• between the first orbit and the nucleus

Answer explanation

A proton is a positively charged particle found in the nucleus of an atom. Therefore, the correct placement for the proton in the model is inside the nucleus.

Tags

NGSS.MS-PS1-1

An atom of chlorine has an atomic number of 17 and an atomic mass of 35. How many protons and neutrons are in the atom?

• A) 17 protons and 17 neutrons

• B) 17 protons and 18 neutrons

• C) 18 protons and 17 neutrons

• D) 18 protons and 18 neutrons

Answer explanation

Chlorine has an atomic number of 17, indicating 17 protons. The atomic mass is 35, which is the sum of protons and neutrons. Therefore, neutrons = 35 - 17 = 18. Thus, the correct answer is B) 17 protons and 18 neutrons.

Tags

NGSS.MS-PS1-1

What charge should be placed in the table for an electron?

• -1

• 0

• +1

• +2

Answer explanation

An electron has a fundamental charge of -1. This negative charge is essential for balancing the positive charge of protons in an atom, making -1 the correct choice for the charge of an electron.

The model shows an atom with subatomic particles labeled V-Z. Which two particles are classified as electrons?

• A) V

• B) W

• C) X

• D) Y

• E) Z

Answer explanation

Electrons are negatively charged subatomic particles. In the model, particles V and Y are labeled as electrons, making them the correct choices. W, X, and Z are not classified as electrons.

Tags

NGSS.MS-PS1-1

Which three subatomic particles are in an atom?

• electron

• ion

• isotope

• neutron

• proton

Answer explanation

An atom consists of three main subatomic particles: electrons, neutrons, and protons. Electrons are negatively charged, protons are positively charged, and neutrons have no charge, making them essential for atomic structure.

Tags

NGSS.MS-PS1-1

Examine the structure of an atom. What are the negatively charged particles?

• electrons

• neutrons

• protons

• quarks

Answer explanation

In an atom, the negatively charged particles are electrons. Neutrons are neutral, protons are positively charged, and quarks are fundamental constituents of protons and neutrons, but do not exist as standalone particles.

Tags

NGSS.MS-PS1-1

An atom has 18 electrons, 15 protons, and 16 neutrons. Which change will cause the atom to have more positively charged particles than negatively charged particles?

• gaining 4 electrons

• gaining 4 protons

• losing 4 protons

• losing 4 neutrons

Answer explanation

The atom has 15 protons and 18 electrons, making it negatively charged. Gaining 4 protons increases the positive charge to 19, resulting in more positive than negative charges (19 protons vs. 18 electrons).

The sum of protons and neutrons in the nucleus of an atom is called the

• valence.

• mass number.

• chemical property.

• electrical charge.

Answer explanation

The mass number is the total count of protons and neutrons in an atom's nucleus. It is a key identifier of an element's isotopes, unlike valence, chemical properties, or electrical charge, which refer to different atomic characteristics.

Ninety-nine percent of the mass of an atom is located in

• the outermost energy level.

• the first energy level.

• the electron clouds.

• the nucleus.

Answer explanation

Ninety-nine percent of an atom's mass is concentrated in the nucleus, which contains protons and neutrons. The outer energy levels and electron clouds contribute little to the overall mass.