Chemistry Unit 1

Cation

positively charged ion (lost electrons)

Anion

negatively charged ion (gained electrons)

Ion

an atom that has gained or lost one or more electrons

Thomson' (AKA Tommy Boi)

Experimented with a cathode ray tube and made a revolutionary discovery regarding the composition of atoms. Based on this observation he concluded that the ray must be composed of negatively charged particles.

This gave rise to a new atomic model called the "plum pudding model" where electrons are spaced throughout a spherical, positively charged medium.

Rutherford

Created the Gold Foil experiment, shooting a beam through the foil. There was a deflection, meaning there must be something very small, dense and positively charged in the center of an atom with electrons moving in an otherwise empty region around the outside.

This discovery led to the development of the first nuclear atomic model, the Bohr Model of the atom. Bohr re-imagined a nuclear model of the atom to be like a solar system with shells of electrons surrounding the nucleus.

Bohr

Theorized in 1913:

Bohr's model shows electrons in specific "shells", also called energy levels.

Each atom has a specific number of these shells, and electrons with more energy are in shells further away from the nucleus.

Proton

Positively charged particle in the nucleus of an atom

Electron

negatively charged particle; located in the space surrounding the nucleus

Neutron

A subatomic particle that has no charge and that is found in the nucleus of an atom

hyphen notation

Element-mass number

nuclear symbol

the superscript indicates the mass number and the subscript indicates the atomic number

average atomic mass

the weighted average of the atomic masses of the naturally occurring isotopes of an element

APE

atomic number = protons = electrons

MAN

Mass Number - Atomic Number = number of Neutrons

subatomic particles

protons, neutrons, electrons

Nucleus

the small, positively charged center of the atom

electron cloud

a region around the nucleus of an atom where electrons are likely to be found

Isotopes

Atoms of the same element that have different numbers of neutrons

Group

A column on the periodic table, tells the amount of valence electrons and has similar properties

period

A horizontal row of elements in the periodic table, tells the amount of energy levels

valence electrons

Electrons on the outermost energy level of an atom

Atom

Smallest particle of an element

percent abundance

how frequently an isotope is found in nature

Mass of protons, electrons, neutrons

1 AMU, ~0 AMU, 1AMU

John Dalton

Created the 5 postulates:

1. Elements are made of tiny particles called atoms

2. All atoms of a given element are identical

3. The atoms of a given element are different from those of any other element

4. Atoms of one element can combine with atoms of other elements to form compounds. A given compound always has the same relative numbers and type of atoms.

5. Atoms are indivisible. Atoms are not created or destroyed in chemical reactions. A chemical reaction simply changes the way atoms are grouped together.

James Chadwick (1932)

Found that neutrons existed in atoms, that help bind the nucleus and the overall atom together. Although hard to detect, since they have no charge, Chadwick found them by using radiation to observe the behavior of atoms.

Werner Heisenberg

A German physicist that speculated that there was no real certainty in where an electron was, and only tendencies. This broke down Newton's dependable laws to only probabilities. To do this, he used gamma rays that he shot towards an atom to capture information on the electron.

Erwin Schrodinger (1926)

Develops mathematical equations to describe the motion of electrons in atoms

His work leads to the electron cloud model

Also stated that electrons are not particles, but waves, so they cannot have a defined shape.

Dimitri Mendeleev

A Russian chemist known for creating the first widely recognized periodic table of elements, which organized elements by increasing atomic mass and predicted the properties of undiscovered elements. He is often referred to as the "father of the periodic table."

Henry Moseley

This British physicist established that elements should be arranged by the number of protons in the nucleus rather than by atomic mass. His work in the early 20th century corrected inconsistencies in the periodic table and laid the foundation for the current understanding of element properties and their relationships. He is known for Moseley's Law, which relates X-ray frequencies to atomic number.

Metals

• Most elements are metals

• Solids at room temperature, except Hg (liquid)

• Malleable - can be bent without breaking

• Ductile - can be stretched into wire

• Lustrous - shiny

• Good conductors of heat and electricity

• High melting points

Nonmetals

• Can be solids, liquids or gases at room temperature (depends on the element)

• Solids are brittle - break easily

• Dull-looking, but sometimes colored

• Poor conductors of heat (insulators)

• Poor conductors of electricity

Metaloids

• Have some properties of metals and some of nonmetals

• Solids at room temperature

• Lustrous

• Brittle - breaks instead of bending

• Semiconductors - conduct electricity only under certain conditions

Alkali Metals

• Group 1A (except H)

• Most reactive metals

• Metallic properties

• React explosively with water

• Never alone in nature

Alkaline Earth Metals

• Group 2A

• Very reactive (but less than alkali metals)

• Metallic properties

• Never alone in nature

Transition Metals

• Groups 3B-2B

• All are solids at room temperature (except Hg)

• Metallic properties

• Form cations with varying charges

Boron Group, Carbon Group, Nitrogen Group

• Groups 3A, 4A, 5A

• Properties vary due to containing metals, nonmetals, and metalloids

Oxygen Group

• Group 6A

• Often found in minerals with other elements

Halogens

• Group 7A

• Most reactive nonmetals

• Means “salt former” because compounds with halogens form salts.

• Highly Toxic

• Exist in all 3 states of matter 

(F and Cl are gases, Br is liquid, I and At are solid)

Noble Gases

• Unreactive

• Do not form compounds easily

• Usually alone in nature

• Often called “inert gases”

Lanthanides

• Found in Period 6

         (between barium and hafnium)

• Highly reactive

• Named for the element lanthanum

Actinides

• Found in Period 7

         (between radium and rutherfordium)

• Highly reactive

• Named for the element actinium

• Elements after uranium (92) are synthetic (created by humans)

Representative/Main Group Elements

Group A

Inner Transition Metals/Rare Earth Metals

Lanthanide and Actinide Series