Unit 1: Intro to Earth/Environmental

Science

Created by: K. Willoughby

Atoms and thePeriodic Table

Study GuideDetermining Shells and Valence Electrons

Elements are the basic building blocks of matter.

Elements and the Periodic Table

Over 100 elements are known.

Smallest particles of matter Have all the characteristics of an element The nucleus is the central part of

an atom and contains• protons, which have positive

electrical charges• neutrons, which have neutral electrical

charges

Atoms

Determining an Atom’s Mass Number and Atomic Number by

Using the Periodic Table

7

14.00674

N

Atomic Number

Element’s symbol

Relative Atomic Mass

Energy levels, or shells• surround the nucleus• contain electrons—negatively charged

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

Bohr Model

Atoms

Isotopes of an element have the same number of protons but varying numbers of neutrons.

Have different mass numbers: the sum of the neutrons plus protons

Many isotopes are radioactive and emit energy and particles.

The mass number is the number of neutrons and protons in the nucleus of an atom.

Isotopes

Why Atoms Bond When an atom’s outermost energy level

does not contain the maximum number of electrons, the atom is likely to form a chemical bond with one or more atoms.• A compound consists of two or more

elements that are chemically combined in specific proportions.

• An ion is an atom that gains or loses electrons.

Mass Number = Number of Protons = Number of Neutrons (Mass # = #P + # N) so M# - #P = # N

Number of Protons = Number of Electrons (P=E)

Atomic Number = Number of Protons A#= #P

http://www.wikihow.com/Find-the-Number-of-Neutrons-in-an-Atom

Periodic Table

Periods • Each row is called a

“period”

1st Period = 1 Shell

2nd Period = 2 Shells3rd Period = 3 Shells

4th Period = 4 Shells

• The elements in each period have the same number of shells

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Groups or Families

• Each column is called a “group”

• Each element in a group has the same number of electrons in their outer orbital, also known as “shells”.

Group 1 = 1 electronGroup 2 = 2 electrons

Group 8 = 8 electrons

Except for He, it has 2 electrons

• The electrons in the outer shell are called “valence electrons”www.chem4kids.com

3, 4, 5, 6, 7

Transition Metals• Transition

Metals have slightly different rules for shells and valence electrons.

• This is something you will learn about in High School Chemistry.

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Determine the number of shells and the number of valence electrons for:

Carbon - C2nd Period = 2 shells

4th Group = 4 valence electrons

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Determine the number of shells and the number of valence electrons for:

Sodium - Na3rd Period = 3 shells

1st Group = 1 valence electron

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Write your answers on your handout

NeName the elementNumber of Shells?Valence Electrons

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2nd Period = 2 shells

Neon

8th Group = 8 valence electrons

Name the elementNumber of Shells?Valence Electrons

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HName the elementNumber of Shells?Valence Electrons

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Hydrogen

Name the elementNumber of Shells?Valence Electrons

1st Group = 1 valence

electron

1stPeriod = 1 shell

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BeName the elementNumber of Shells?Valence Electrons

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2nd Period = 2 shells

Beryllium

2nd Group = 2 valence electrons

Name the elementNumber of Shells?Valence Electrons

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SName the elementNumber of Shells?Valence Electrons

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3rd Period = 3 shells

Sulfur

6th Group = 6valence electrons

Name the elementNumber of Shells?Valence Electrons

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KName the elementNumber of Shells?Valence Electrons

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4th Period = 4 shells

Potassium

1st Group = 1 valence electrons

Name the elementNumber of Shells?Valence Electrons

Potassium

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HeName the elementNumber of Shells?Valence Electrons

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1st Period = 1 shellsHeliu

m8th Group = 8 valence electrons

Name the elementNumber of Shells?Valence Electrons

• Helium is the exception in Group 8.

• Since it has just one shell, that shell can only fit 2 electrons instead of 8.

• It is in this group because all the elements have a full outer shell.

Be sure to have all your answers on the

worksheet.

End of Study Guide