An atomic model shows 19 protons, 20 neutrons, and 19 electrons. What is the mass number of the atom?(1 point)

Question

Responses

39
39

19
19

58
58

20
20
Check answer

Answer 1

The mass number of an atom is the sum of the number of protons and neutrons. In this case, the atom has 19 protons and 20 neutrons.

Mass number = Number of protons + Number of neutrons Mass number = 19 + 20 = 39

Therefore, the mass number of the atom is 39.

Answer 2

To create a molecular model, a student will use blue spheres to represent nitrogen (N) and white spheres to represent hydrogen (H). Which option correctly describes a model of ammonia, NH3?(1 point)
Responses

three blue spheres and one white sphere
three blue spheres and one white sphere

three blue spheres and three white spheres
three blue spheres and three white spheres

one blue sphere and three white spheres
one blue sphere and three white spheres

one blue sphere and one white sphere

Answer 3

Ammonia (NH₃) consists of one nitrogen atom and three hydrogen atoms. In the molecular model, the nitrogen atom is represented by one blue sphere and the hydrogen atoms are represented by three white spheres.

Therefore, the correct description of a model of ammonia (NH₃) is one blue sphere and three white spheres.

Answer 4

A ball-and-stick model of a molecule of formaldehyde, CH2O, is made from the following components:

one black ball
one red ball
two white balls
three sticks
What do the sticks represent?

(1 point)
Responses

carbon atoms
carbon atoms

oxygen atoms
oxygen atoms

bonds between atoms
bonds between atoms

hydrogen atoms

Answer 5

In a ball-and-stick model, the sticks represent the bonds between atoms. In the case of formaldehyde (CH₂O), the sticks would illustrate how the atoms are connected to each other.

Therefore, the correct answer is bonds between atoms.

Answer 6

Potassium and nickel are in the same row of the periodic table. What do these elements have in common?(1 point)
Responses

They have similar physical properties.
They have similar physical properties.

They have similar reactivity.
They have similar reactivity.

They have the same number of electron shells.
They have the same number of electron shells.

They have the same number of valence electrons.

Answer 7

Potassium (K) and nickel (Ni) are both located in the same row (period) of the periodic table. What they have in common due to being in the same period is that they have the same number of electron shells.

Therefore, the correct response is They have the same number of electron shells.

Answer 8

Why do elements that are in the same group of the periodic table share similar properties?(1 point)
Responses

They all have the same number of electrons in the outer shell.
They all have the same number of electrons in the outer shell.

They all have the same atomic mass.
They all have the same atomic mass.

They are all very reactive with other elements.
They are all very reactive with other elements.

They are all metals.

Answer 9

Elements that are in the same group (or column) of the periodic table share similar properties primarily because they all have the same number of electrons in the outer shell (also known as valence electrons). This similarity in valence electron configuration leads to comparable chemical behaviors and reactivities.

Therefore, the correct response is They all have the same number of electrons in the outer shell.

Answer 10

Suppose 20 atoms of hydrogen (H) react with chlorine (Cl) to produce 20 molecules of hydrochloric acid (HCl). According to the law of conservation of matter, how many atoms of chlorine reacted with the hydrogen?(1 point)
Responses

40
40

10
10

0
0

20

Answer 11

According to the law of conservation of matter, matter cannot be created or destroyed in a chemical reaction. In the chemical reaction where hydrogen (H) reacts with chlorine (Cl) to produce hydrochloric acid (HCl), each molecule of HCl is composed of one hydrogen atom and one chlorine atom.

Since 20 molecules of HCl are produced, this means that 20 chlorine atoms are needed to react with the 20 hydrogen atoms.

Therefore, the correct response is 20.