The Atom Whats Inside an Atom The Nucleus

The Atom

What’s Inside an Atom

The Nucleus • The nucleus is the small dense, positively charged center of the atom. It contains most of the atom's mass.

The Proton Charge: positive Mass: 1 amu Location: nucleus

The Neutron Charge: Neutral Mass: 1 amu Location: Nucleus

The Electron Charge: negative Mass: almost zero Location: electron cloud (outside the nucleus)

The Atomic Number • The atomic number is the number of protons in the nucleus of an atom • The number of protons determines the element Atomic Number

Mass Number • The mass number is the sum of the protons and neutrons in an atom (measured in amu) Mass Number

Isotopes • Isotopes are atoms that have the same number of protons, but have different numbers of neutrons.

Calculating the number of Neutrons in an Atom. How many neutrons are in a Carbon atom with an atomic weight of 14. Atomic weight is the number of protons and neutrons. The atomic number is the number of protons…………. so, 14 – 6 = 8 neutrons

Average Atomic Mass • The average atomic mass is the weighted average of the masses of all the naturally occurring isotopes of an element.

Calculating the Average Atomic Mass What is the average atomic mass of Chlorine; if 75% is chlorine-35, and 25% is chlorine-37? (35 X. 75) + (37 X. 25) = (26. 25) + (9. 25) = 35. 5 amu