Subatomic Particles
What are the three main subatomic particles found in an atom?
Proton, neutron, electron
What is the center of the atom called?
The nucleus
Which force attracts negatively charged electrons to the positively charged nucleus?
Electromagnetic force
What are the regions around the nucleus where electrons are found called?
Energy levels or shells
True or False: The identity of an atom is determined by its number of neutrons.
False
Which particle determines the identity of an element?
Proton
What is found in the electron cloud?
Electrons
What type of force holds protons and neutrons together inside the nucleus?
Strong nuclear force
What do we call electrons in the outermost energy level?
Valence electrons
Which particle changes when an atom becomes an ion?
The electrons
Which subatomic particle has negligible mass and a negative charge?
Electron
Why is the atom said to be “mostly empty space”?
Because electrons orbit far from the dense nucleus
Why don’t protons fly apart even though they repel each other?
The strong nuclear force overcomes their repulsion
How many valence electrons does a carbon atom have?
Four
If an atom has 11 protons and 10 electrons, what is its charge?
+1
Where in the atom are neutrons located?
In the nucleus
If an atom has 8 protons, 8 neutrons, and 8 electrons, what is its mass number?
16
What happens when like charges are near each other?
They repel
Why are valence electrons important?
They determine how atoms bond and react chemically
Which has more mass—an electron or a proton?
A proton
How is the number of electrons related to the number of protons in a neutral atom?
They are equal
How does the nucleus differ from the electron cloud in density and mass?
The nucleus is dense and contains nearly all the mass; the electron cloud is diffuse and light
How do the electromagnetic and strong nuclear forces work together to stabilize the atom?
Electromagnetic force keeps electrons bound; strong nuclear force keeps the nucleus intact
As you move across a period from left to right, what happens to the number of valence electrons?
It increases by one each time until the shell is full
Explain why electrons stay near the nucleus even though they are repelled by each other.
The attraction to the positively charged nucleus is stronger than the repulsion between electrons