Basics of an atom

(nucleus)

Most of an atom consists of empty space.

(nucleus)

If the nucleus were the size of a dime, the furthest electron would be more than a mile away.

(nucleus)

Protons have a positive electrical charge.

(nucleus)

Protons have a positive electrical charge.The number of protons determines the atomic number.

(nucleus)

Neutrons have no electrical charge and have no role in chemical reactions.

(nucleus)

The number of neutrons can vary, although there are often the same number of neutrons as there are protons.

(nucleus)

Because the number of neutrons can vary, not every atom of the same element will have the same mass.

(nucleus)

Electrons have a negative charge.

(nucleus)

Electrons have a negative charge. There is one electron for every proton, giving an atom an overall neutral charge.

(nucleus)

Electrons move so fast around the nucleus that they can’t be seen, like the moving blades of a fan.

Valence electrons are furthest from the nucleus. They determine whether two or more atoms can form a chemical bond.

(nucleus)

A chemical bond forms when valence electrons move between atoms or are shared between them.

The number of valence electrons can range from one to eight.

Sodium Argon

Valence electron shell

The number of valence electrons can range from one to eight.Atoms are most stable (least reactive) when they have either zero or eight valence elections.

Sodium Argon

Valence electron shell

Chemists use a Lewis electron dot diagram to show how many valence electrons each atom has

Chemists use a Lewis electron dot diagram to show how many valence electrons each atom has

For more, see http://www.touchspin.com/chem/DisplayTable.html

C Cl H Ca

Na Ne O

Possible two-atom compounds

C Cl H Ca

Na Ne O

Possible two-atom compounds

• Hydrogen and chlorine

• Name at least two more

Atoms are too small to be measured in grams, so they are measured in the atomic mass unit, or amu.

Atoms are too small to be measured in grams, so they are measured in the atomic mass unit, or amu.

• One proton is about ____ amu.

Atoms are too small to be measured in grams, so they are measured in the atomic mass unit, or amu.

• One proton is about one amu.

Atoms are too small to be measured in grams, so they are measured in the atomic mass unit, or amu.

• One proton is about one amu.

• One neutron is about one amu.

Atoms are too small to be measured in grams, so they are measured in the atomic mass unit, or amu.

• One proton is about one amu.

• One neutron is about one amu.

• One electron is about 1/2000 amu.

Atoms are too small to be measured in grams, so they are measured in the atomic mass unit, or amu.

• One proton is about one amu.

• One neutron is about one amu.

• One electron is about 1/2000 amu.

• Carbon (atomic #6) weighs about ___ amu.

Atoms are too small to be measured in grams, so they are measured in the atomic mass unit, or amu.

• One proton is about one amu.

• One neutron is about one amu.

• One electron is about 1/2000 amu.

• Carbon (atomic #6) weighs about 12 amu.