Atomic Structure &

Elements

Size of the Atom

►Average sized atom 0.00000003 cm►Aluminum foil 50,000 atoms thick►1 penny 20,000,000,000,000,000,000,000 atoms of

copper and zinc (20 thousand billion billion

Parts of the Atom

►Proton- Positive (+) particle (nucleus)►Determines the element

►Neutron- Neutral (0)particle (nucleus)►Nucleus- Central, dense core of atom

Protons and neutrons are found in the nucleus of the atom and make up almost all the mass of the atom.

►Electron- Negative (-) particle (electron cloud around nucleus)

Modern view of the atom

►The atom is mostly empty space►Nucleus – Protons and neutrons►Electron cloud is the area where

electrons of an atom are most likely found.

Counting the Pieces Review

►Atomic Number= Number of protons►Atomic Mass= Protons + Neutrons►# of protons determines kind of atom. ►Neutral Atom= the same number of

protons and electrons ►All particles in the atom have mass. ►Proton= 1amu (atomic mass unit)►Neutron= 1amu►Electrons have a very small mass

Atoms and Elements►Atoms of different elements are

different Determined by # of protons

►Atoms of the same element are almost the same Isotopes have a different number of

neutrons Does not change the charge of the atom. Occur naturally and share the same

properties Some are unstable and the nucleus can

change composition (radioactive isotopes)

Isotope

Naming the Isotopes

►32He

►42He

► 126C

► 146C

► 23592U

► 23992U

Mass number of this atom

Atomic numberof the element

This atom of hydrogen has two protons and one

neutron. 1 + 1+ 1= 3 amu

Atomic MassAtomic Number

Element Symbol

Write the isotopes of Hydrogen shown.

11H

21H

31H

Atomic Mass

►The atomic mass is not a whole number because it is a weighted average of all the oxygen isotopes in the world.

Measuring Atomic Mass

►Atomic mass is measured in Atomic Mass Units or AMU’s and is the addition of the number of Protons and Neutrons in an atom. Same number of electrons &

Protons Neutrons different.

Atomic Mass=________

Atomic Mass=________

Elements Chapter 4 Section 1

►An element is a pure substance that cannot be broken down into simpler substances and have the same properties

► Classified by properties►Grouped into categories using these properties►Metals►Metalloids►Non-metals

Metals Shiny Good conductors of thermal energy Good conductors of electrical current Malleable Ductile Located on the left side of the periodic table

Three Categories of Elements

Nonmetals Dull Poor conductors of thermal energy Poor conductors of electric current Brittle/ unmalleable Located on the right side of the periodic table

Three Categories of Elements

Metalloids Sometimes called semi-metals or semiconductors Can be shiny or dull Somewhat malleable Somewhat ductile Some are good conductors of thermal energy and electrical

current

Three Categories of Elements