Chapter 6-2part 1

The Atom

The Parts of an Atom

• Almost all atoms are made of the same three parts.

• These particles are protons, neutrons, and electrons.

Subatomic Particles• Protons, neutrons, and electrons are

called subatomic particles because they are smaller than an atom.

• The number of particles determine the properties of the atom.

The Nucleus• Protons are positively charged particles.• Neutrons are particles with no charge.• Atomic mass is the weight of the

nucleus.• You find the atomic mass by adding the

protons and neutrons together.• Example: Carbon has 6 protons and 6 neutrons, so its atomic mass is 12.

OUTSIDE THE NUCLEUS

• Electrons are negatively charged particles in atoms.

• Electrons are outside the nucleus in electron clouds.

• The mass of an electron is so small it is thought of as zero.

• Charges of protons and electrons are opposite but equal.

• The charges cancel each other out so the atom’s charge is neutral.

ATOMS AND ELEMENTS• There are 110 different elements.• Each atom is different from the others.

THE SIMPLEST ATOM

• The simplest atom has just one proton and one electron.

• That element is hydrogen.

THE ROLE OF NEUTRONS• Helium has 2

protons.• Positively charged

protons repel each other.

• Neutrons are there to keep this from happening and keeps the nucleus together.

BUILDING BIGGER ATOMS• You could build bigger atoms by using

more protons, neutrons, & electrons.• Atoms have an equal number of

protons and electrons.• Atoms do not have to have an equal number of protons and neutrons.

PROTONS & ATOMIC NUMBER

• The number of protons in the nucleus of an atom is the atomic number of that atom.

• The atomic number of each element is listed on the periodic table.

6

CCarbon

12.01

Atomic number

Atomic mass = # of protons and neutrons

LET’S TRY IT!

•LAB: M & M Nucleus