An atomic model shows 19 protons, 20 neutrons, and 19 electrons. What is the mass number of the atom?(1 point)
Responses
19
19
39
39
20
20
58
The mass number of an atom is equal to the sum of its protons and neutrons. In this case, the atom has 19 protons and 20 neutrons, so the mass number would be 19 + 20 = 39.
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
oxygen atoms
oxygen atoms
bonds between atoms
bonds between atoms
carbon atoms
carbon atoms
hydrogen atoms
hydrogen atoms
The sticks in a ball-and-stick model represent the bonds between atoms. In this case, the molecule CH2O consists of one carbon atom (represented by a black ball), two hydrogen atoms (represented by two white balls), and one oxygen atom (represented by a red ball). The sticks connect these atoms and represent the bonds between them. Therefore, the correct answer is "bonds between atoms".
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
one blue sphere and three white spheres
one blue sphere and three white spheres
one blue sphere and one white sphere
one blue sphere and one white sphere
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
Ammonia, NH3, consists of one nitrogen atom (N) and three hydrogen atoms (H). Therefore, to create a molecular model of ammonia, the student would use one blue sphere to represent the nitrogen atom and three white spheres to represent the hydrogen atoms. So, the correct answer is "one blue sphere and three white spheres".
To determine the mass number of an atom, we need to add the number of protons and neutrons together. In this case, we have 19 protons and 20 neutrons. Adding these two numbers together, we get a total of 39.
So, the correct answer is 39.