Atomic Structure Hmmmm… Imagine cutting a gold bar in half. Then cut in half again. …and again. How small could you cut up that gold and it still be gold?

Atoms An atom is the smallest particle into which an element can be divided and still be the same substance. Atoms make up elements and elements combine to form compounds.

element – Substance made up atom – The smallest particle that can exist on its own. element – Substance made up of only one type of atom. compound – Substance made up of two or more different elements that are chemically joined together.

Atoms An atom is made of 3 parts: Protons (+) Neutrons (neutral) Electrons (-) Protons and neutrons make up the nucleus of the atom Electrons orbit around the nucleus like planets around the sun

Notice that the electrons are not apart of the nucleus Subatomic Particles Protons Neutrons Electrons Nucleus Notice that the electrons are not apart of the nucleus

Protons Positive Charge Atomic Structure Protons Positive Charge The number of protons determines which element it is. All elements have different numbers of protons 1 amu Composed of quarks

Rutherford’s Gold Foil Experiment 1919 In Rutherford’s gold foil experiment (1871-1937),positively charged particles were aimed at atoms of gold. mostly went straight through the atoms. were deflected only occasionally. Conclusion: There must be a small, dense, positively charged nucleus in the atom that deflects positive particles that come close. Rutherford proposed that the atom must consist mainly of empty space with the mass concentrated in a tiny central core—the nucleus

What makes one element different from another element? Number of protons. Atomic Structure

Neutron Neural charge Located in the nucleus 1 amu Composed of quarks Atomic Structure Neutron Neural charge Located in the nucleus 1 amu Composed of quarks Neutrons were discovered by James Chadwick in 1932. Have mass like proton, but no charge.

Electrons Smallest subatomic particle. 1/1800 the mass of a proton. Atomic Structure Electrons Smallest subatomic particle. 1/1800 the mass of a proton. Orbit nucleus. Negative Charge

Discovery of the Electron-Thomson 1897

Electrons are found in different levels around the nucleus. Atomic Structure Electrons are found in different levels around the nucleus. These are called Energy Levels or shells. Each energy level also has “sublevels” or orbitals

Atomic Structure

Electrons are found in the surrounding the nucleus. Atomic Structure Electrons are found in the Electron cloud surrounding the nucleus.

Each Energy Level Can Hold A Certain Number of Electrons! Atomic Structure Each Energy Level Can Hold A Certain Number of Electrons! Only TWO on the first level!

Atoms Activity: Use your notes to draw an atom and label its parts. 3 Protons (+) 3 Neutrons (neutral) 3 Electrons (-) Nucleus Your drawing should fill an entire page and it should be colored/shaded.

Atomic Structure

Atomic Structure

1 Atomic Mass Sum of Protons & Neutrons Atomic Number Atomic Structure Atomic Number Number of Protons 1 H Atomic Mass Sum of Protons & Neutrons 1 The # of Protons determines the identity of an element. All elements have different number of protons.

How can I find out how many electrons an atom has? Atom= neutral So, the number of protons = electrons. Atomic number tells you the number of protons................. So, it also tells you the number of electrons! Atomic Structure

Isotopes

Isotopes iso = same atoms of the same element with different numbers of neutrons have different atomic masses but the same atomic number some are stable, some are radioactive (carbon-12 and carbon-14)

Most isotopes are stable but radioactive isotopes are unstable and break down into more stable forms by emitting particles and energy (radiation). Radiation can be detected, so radioactive isotopes are useful as labels in scientific research and medical diagnostic procedures.

Let’s Do some practice problems 