An atom is often referred to as the building block of matter. Atoms have a nucleus surrounded by an electron cloud

An atom is often referred to as the building block of matter. Atoms have a nucleus surrounded by an electron cloud

• An atom is often referred to as the building block of matter. Atoms have a nucleus surrounded by an electron cloud

• Atoms are composed of smaller subatomic particles in an atom. The proton, neutron, and electron.

• Each element is composed of one type of atom and can not be broken down into a simpler substance

Nucleus - Small, dense, positively charged center of the atom which contains most of the atom’s mass

• Nucleus - Small, dense, positively charged center of the atom which contains most of the atom’s mass
• The nucleus contains subatomic particles that have certain characteristics:
• Protons (p+) - positively charged particles in the nucleus of the atom, contribute to the atom’s mass
• Neutrons (no)- particles in the nucleus that have no charge, but contribute to the atom’s mass NEUTRAL

Electron cloud - an area encircling the nucleus where electrons are likely to be found

• Electron cloud - an area encircling the nucleus where electrons are likely to be found
• The cloud contains energy levels
• electrons (e-)are negatively charged particles located in specific energy levels
• energy levels completely surround the nucleus
• there is a specific order for the electrons to fill the energy levels

Energy levels completely surround the nucleus

• Energy levels completely surround the nucleus

valence electrons are in the outermost energy level and are the electrons involved in bonding

• valence electrons are in the outermost energy level and are the electrons involved in bonding
• valence electrons determine the number of bonds an atom can form
• an atom is most stable when its outermost energy level is full

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

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

• The number of protons (+) equals the number of electrons (-) in a neutral atom

• The mass number is the mass of the protons plus the mass of the neutrons

• mass is reported in the SI units atomic mass units (amu)
• Protons and neutrons each are given an amu of 1
• Electrons have a mass of nearly zero

The mass number of an atom is for a particular isotope of that element

• The mass number of an atom is for a particular isotope of that element

• Mass number is the total number of protons and neutrons in the nucleus

• Example for C-12:

• 6 protons + 6 neutrons= 12
• 12 is the mass number for Carbon-12
• *13 is the mass number for Carbon-13 and comes from C-13 having 6 protons and 7 neutrons