Name: ______________________________
Date: ___________________ Core: ______
Visible Atom
Essential Learnings

A. The smallest particle of an element and the basic building block of all matter is called an atom. It is made up of 3
subatomic particles called:
1. protons
2. neutrons
3. electrons
B. A proton is a positively charged particle with a mass of 1 atomic unit (amu).
C. A neutron has no charge (it is neutral) and has a mass of 1 amu.
D. Electrons are infinitely smaller than the other subatomic particles and have almost no mass. They are negatively
charged and are found in a “cloud” around the center.
E. The protons and neutrons of the atom are grouped together in the center or nucleus which accounts for almost
all of the entire mass of the atom.
F. Scientists use models to help explain and understand the structure of the atom because it is too small to be seen.
G. The electron cloud model shows the locations of the electrons as they move around the nucleus in their energy
levels. The number of valence electrons in the outermost energy level determines how likely it is to combine
with other elements.
H. Each box in the periodic table of elements represents one element and contains its name, symbol, atomic
number, and atomic mass.
I.
The atomic number is used to determine the number of protons.
J. The atomic mass is used to calculate the number of neutrons by subtracting the number of protons (atomic
number) from it.
K. The outermost energy level (valence) electrons can be determined by:
the group/family to which each element belongs (except transition metals)
L. Ions are atoms which have gained or lost electrons. If they gain 1 or more electrons, then the atom will have a
negative charge. If they lose 1 or more electrons, then the atom will have a positive charge.
Name: ______________________________
Date: ___________________ Core: ______
Practice
Using your periodic table draw two models in the space below:
Make sure you show: electrons, protons, neutrons, valence electrons, nucleus and electron cloud.
1. Calcium (Ca)
2. Iodine (I)
Protons—53
Neutrons—74
Electrons:
Total—53
Valence—1
In the cloud—52
Protons—20
Neutrons—20
Electrons:
Total—20
Valence—2
In the cloud—18
Matching
A. positive ion, +1
C silicon (Si): 14 protons, 14 neutrons, 10 electrons
B. negative ion, -3
D iodine (I): 53 protons, 74 neutrons, 54 electrons
C. positive ion, +4
E sulfur (S): 16 protons, 16 neutrons, 18 electrons
D. negative ion, -1
A potassium (K): 19 protons, 20 neutrons, 18 electrons
E. negative ion, -2
F barium (Ba): 56 protons, 81 neutrons, 54 electrons
F. positive ion, +2
B arsenic (As): 33 protons, 42 neutrons, 36 electrons
Explain
1.
Why is “B” (from matching) a negative ion?
the atom has gained electrons, so it has 3 more electrons (negative) than protons (positive), therefore it
has an overall negative charge
2. Why is “C” (from matching) a positive ion?
the atom has lost 4 electrons, so it has 4 more protons (positive) than electrons (negative), therefore it
has an overall positive charge