Atomic Structure and Chemistry. What is matter? Matter is anything that takes takes up space and has mass. May or may not be visible (example.... air)

Atomic Structure and Chemistry

What is matter? Matter is anything that takes takes up

space and has mass.•May or may not be visible (example.... air)

What is an element?

•Examples: Gold, Mercury, Sulfur, & Hydrogen

•Over 100 elements represented on the Periodic Table of Elements

A chemical element is a pure substance that consists entirely of one

type of atom.

Three types of elements

• Metal - An element with luster (shine), that is a good conductor of heat and electricity, is malleable (may be shaped or pounded) and ductile (may be stretched into wire)

• Nonmetal - An element that is a gas or brittle solid at room temperature, and does not conduct heat or electricity well

•Metalloid - The element that shares properties of metals and nonmetals, and may conduct small amounts of electricity and heat

What is an atom? An atom is the basic unit of matter... It is

the smallest particle of an element that

retains the physical and chemical

characteristics of that element.

•Composed of 3 subatomic particles... 1) Protons 2) Neutrons 3) Electrons

SubAtomic particles

• Protons - Positively charged particles found in the nucleus of the atom that make up about one half of the mass of an atom

• Neutrons - Particles without charge found in the nucleus of the atom that make up about one half of the mass of an atom

• Electrons - Negatively charged particles orbiting the nucleus of the atom with 1/1840 the mass of a proton

More about atoms...

•Atomic number = # Protons = # Electrons

•Atomic Mass = # Protons + # Neutrons

Why is that important?

• # Protons = # Electrons, therefore individual atom is electrically neutral

• Like charges repel... Electrons maintain space between one another. What about protons?

• Neutrons act as buffer zones between positively charged protons

• Larger number of protons requires even more neutrons to separate positively charged particles (so # Protons does not always equal # Neutrons)

Energy levels in the electron cloud

•Electrons are found orbiting the nucleus in the electron cloud

•Different areas where electrons may be found within an electric cloud are known as energy levels

•Orbitals in the electron cloud closest to the nucleus have the lowest energy level... Orbitals farthest from the nucleus have the highest energy level

•Orbitals farthest from the nucleus can hold the most electrons because it allows for the most space between the electrons

Energy levels in the electron cloud

Like charges repel•Electrons are negatively charged and repel other electrons. So they orbit in different directions and regions to stay as far away from each other as possible...

Election configurations

•Due to closer proximity to the nucleus, it is easier to fill an spherical orbital of a higher energy level than an irregularly shaped orbital with a lower energy level. So an s-orbital of the 4th energy level will fill with electrons before a d-orbital of the 3rd energy level...

Bohr model of the atom

• Niels Bohr developed a model that shows the energy level position of electrons around the nucleus

•Known as a Bohr Model

Energy levels in the electron cloud

• Even though the third level can hold 18 electrons, if 8 electrons are present, the atom will be stable

• This holds true for the fourth, fifth, sixth, and seventh levels as well...

•This idea is represented by an electron dot diagram, formally known as a Lewis Dot Structure...

Lewis dot structure & the Bohr model...

Lewis dot structure

• A Lewis Dot Structure is a representation of the atom that only shows valence electrons (the number of electrons in the outer orbital), with a maximum number of eight electrons in the outer shell

• This electron dot model shows the tendency of the atom to react with other atoms due to it's need to become stable by filling its outer orbital with eight electrons (known as the Octet Rule), thus forming a compound

Lewis dot structure & the representative elements

What is a compound?

•Examples include water (H2O ), table salt (NaCl), and glucose (C6H12O6)

•The chemical formula expresses the type of atoms combined and number of each type of atoms...

A compound is a substance formed by the chemical combination of two or more elements in

definite portions.

What is a chemical reaction?

•When 2 atoms of Hydrogen join with an atom of Oxygen, water is formed...

•Water forms via a chemical reaction

•Chemical reactions occur by the breaking and/or forming of bonds between atoms

Lewis dot structure & compound formationLewis Dot Structures

show the electrons that form bonds between atoms in chemical

reactions, while trying to fill their outer orbitals, forming

compounds via the reactions

So this electron dot

model shows the way atoms react with other

atoms...

Types of Chemical bonds

• Ionic bonds - electrons are donated by one atom and accepted by another

• Covalent bonds - electrons are shared between atoms

• Polar Covalent bonds - electrons are shared unevenly between atoms, resulting in polarity of the molecule

• Hydrogen bonds - weak attractive force between oppositely charged atoms

• Metallic bonds - electrons are shared between many other metal atoms

Ionic bonds

Electrons are donated by one atom and accepted by the other... The resulting charged atoms are now

called ions.

Formation of Ions Ions are electrically charged because the

balance of charge between protons and electrons has been

upset by the net loss and gain of electron(s)

Covalent bonds

Electrons are shared between atoms

Multiple covalent bonds

Multiple electrons are shared between atoms, resulting in double and triple covalent bonds

Polar covalent bonds

Electrons are shared unevenly between atoms, resulting in polarity

of the molecule

Hydrogen bonds

Weak attractive force between oppositely charged atoms

Hydrogen bonds are important in biology

•Water is necessary for life reactions to occur

•H-bonding helps proteins maintain their structure and therefore, function

•H-bonding allows DNA strands to separate and rejoin easily

Metallic bonds

Electrons are shared between many metal atoms, as if the atomic nuclei are floating in a

sea of electrons

Mickey molecule...