Atomic Structure

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Most of the volume of the atom is empty space

Helium-4

Image: User Yzmo Wikimedia Commons.

Slide 17

About Quarks…

Protons and neutrons are NOT fundamental particles.

Protons are made of two “up” quarks and one “down” quark.

Neutrons are made of one “up” quark and two “down” quarks.

Quarks are held together by “gluons”

Images: Arpad Horvath, Wikimedia Commons.

Slide 18

Isotopes

Isotopes are atoms of the same element having different masses due to varying numbers of neutrons.

Slide 19

Atomic Masses

Atomic mass is the average of all the naturally isotopes of that element.

Carbon = 12.011

Slide 20

Atomic Number

Atomic number (Z) of an element is the number of protons in the nucleus of each atom of that element.

Slide 21

Mass Number

Mass number is the number of protons and neutrons in the nucleus of an isotope.

Mass # = p+ + n0

8

8

18

18

Arsenic

75

33

75

Phosphorus

15

31

16