ATOMIC

STRUCTURE

• ATOM´S• ELECTRONS, PROTONS

AND NEUTRONS• ATOMIC AND MASS

NUMBER • ISOTOPES OF THE

ELEMENT

Dalton´s Atomic Theory

• All elements are compound of submicroscopic indivisible parts called atoms.

• Atoms of the same element are identical. The atoms of any one element are different from those of any other element.

• Atoms of different elements can physically mix together or can chemically combine with one another in simple whole number ratios to form compounds.

• Chemical reactions occur when atoms are separated, joined, or rearranged. However atoms of one element are never changed into atoms of another element as a result of a chemical reaction

Atomic Number• Protons and neutrons form the small dense

nucleus.• Electrons occupy most of the atoms volume.

• Atoms differ by the number of protons in their nucleus.

• Atomic Number: is the number of protons in the nucleus of the atom of that element. (this number identief the element)

• Atoms are electrically neutral # of protons = # of electrons

Related Problems• The element nitrogen (N) is atomic number 7.• How many protons and electrons are in a nitrogen

atom?

Why is an atom electrically neutral?What is the relationship between the number of protons and the atomic number of an atom?

Mass Number• Mass Number is the total number of protons and

neutrons in the nucleus.• An atoms composition can be determined from its

atomic number and mass number

# of Neutrons = Mass # - Atomic #

Related Problems• How many protons, electrons, and neutrons are in

the following atoms?

ELEMENT ATOMIC NUMBER MASS NUMBER

BERILLIUM 4 9

NEON 10 20

SODIUM 11 23

Related Problems• Complete the following table:

ATOMIC #

MASS #

# PROTONS

# OF NEUTRONS

# ELECTRONS

ELEMENTSYMBOL

9 ______ ______ 10 ______ ______

______ ______ 14 15 ______ ______

______ 47 ______ ______ 22 ______

______ 55 25

______

______ ______