Atomic models and periodic table, Study notes of Environmental science

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Science

Science Review- Atomic models and Periodic Table

Atom is at neutral state, meaning that there are same number of protons and electrons. Protons: (+) charge *positive Electrons: (-) charge *negative Neutrons: (-+) charge *neutral Rutherford: 1911 -He used a gold foil experiment to discover his theories. His theories: -Atom is big and almost empty relative to the nucleus. *because alpha particles went through gold foil. -Atom has small dense nucleus in the middle. *alpha particles rarely repelled off nucleus. -Nucleus is positively charged. *alpha particles are positively charged and repel off nucleus. -Electrons revolve around the nucleus. *electrons are attracted to the positively charged nucleus.

Bohr: 1913

-Agreed with all theories of

Rutherford except for the

placement of electrons.

Bohr’s theory on electrons:

Electrons were found on orbits

which Were moving continually.

The orbits can hold a specific

number of electrons.

Orbit 1: 2 electrons Orbit 2: 8 electrons Orbit 3: 8 electrons Orbit 4: 2 electrons * Chadwick: 1932

• Agreed with Rutherford-Bohr model, believed something was missing in the nucleus. WHAT IS MISSING FROM MODEL AND WHY ARE THEY NECESSARY? Neutrons are missing. They are necessary because they prevent the p+ from repelling off each other and causing nucleus to be unstable.

HOW TO CALCULATE # OF NEUTRON?

Specific family or group names Families 3-6: group names are named after first element in group. Example: group 3 is called boron group.

Elements vs compounds:

Groups 1-7 are always found as compounds, not as elements in

everyday use. Metals and nonmetals will chemically bond and

form a compound. Once the elements bond, a stable compound is

formed.

Group 8 is always found as element, never as compound. This is

because their orbits are already full and stable.