An atomic model shows 19 protons, 20 neutrons, and 19 electrons. What is the mass number of the atom? (1 point)
O 20
O 19
O 39
O 58
The mass number of an atom is equal to the sum of its protons and neutrons. Therefore, the mass number of this atom is 19 protons + 20 neutrons = 39.
So, the correct answer is O 39.
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, NH? (1 point)
O one blue sphere and one white sphere
• three blue spheres and one white sphere
O one blue sphere and three white spheres
• three blue spheres and three white spheres
The correct answer is: three blue spheres and one white sphere.
Ammonia (NH3) consists of one nitrogen atom (N) and three hydrogen atoms (H). In the molecular model, nitrogen is represented by blue spheres and hydrogen is represented by white spheres. Therefore, we would need three blue spheres to represent the nitrogen atoms and one white sphere to represent the hydrogen atom.
So, the correct option is: three blue spheres and one white sphere.
wrong
I apologize for the incorrect response.
The correct model for ammonia (NH3) would be one blue sphere and three white spheres. In ammonia, there is one nitrogen atom (N) and three hydrogen atoms (H). The nitrogen atom would be represented by a blue sphere, and the three hydrogen atoms would be represented by three white spheres.
So, the correct option is one blue sphere and three white spheres.
A ball-and-stick model of a molecule of formaldehyde, CH,O, is made from the following components:
• one black ball
• one red ball
• two white balls
• three sticks
What do the sticks represent?
(1 point)
• hydrogen atoms
• carbon atoms
• oxygen atoms
• bonds between atoms
The sticks in a ball-and-stick model represent the bonds between atoms.
In the case of formaldehyde (CH2O), there are three sticks, representing the bonds between carbon (C) and hydrogen (H) atoms, carbon (C) and oxygen (O) atoms, and oxygen (O) and hydrogen (H) atoms.
So, the correct answer is: bonds between atoms.
Potassium and nickel are in the same row of the periodic table. What do these elements have in common? (1 point)
]
• They have the same number of valence electrons.
• They have similar physical properties.
• They have the same number of electron shells.
• They have similar reactivity.
Potassium and nickel do not have the same number of valence electrons, as potassium has 1 valence electron and nickel has 2 valence electrons. Therefore, the first option, "They have the same number of valence electrons," is incorrect.
Potassium and nickel do not have similar physical properties as they are located in different groups and have different atomic properties. Therefore, the second option, "They have similar physical properties," is incorrect.
Potassium and nickel do not have the same number of electron shells, as potassium has 4 electron shells and nickel has 4 electron shells. Therefore, the third option, "They have the same number of electron shells," is incorrect.
However, potassium and nickel do have similar reactivity as they both belong to the same group (Group 1 and Group 10, respectively) and exhibit similar patterns of reactivity. Therefore, the correct answer is: They have similar reactivity.