Chemistry of LifeChapter 2

Warm Up 8/20Try to recall the following information without referencing your textbook or a friend

What is an atom?

What is an element?

What differentiates one element from another?

What are protons, neutrons and electrons?

AnswersAtom: basic unit of matter

Made up of 3 smaller particlesNeutrons- no charge “neutral.” Found in nucleusProtons- positive charge. Found in nucleusElectrons- negative charge. Tiny. Orbit nucleus in a 3D “electron cloud”

Element: a specific kind of atomDetermined by number of PROTONS

Examples?

Element name

Atomic Number

Element Symbol

Atomic Mass

Atomic Number and Atomic mass

Atomic NumberNumber of protons in that elementNeutral atoms also have that same number of electrons

Atomic massMass of protons and neutrons*usually about double the atomic number because there are typically the same number of protons and neutrons

SummaryFor our purposes, a typical, stable atom has the same number of protons, neutrons and electrons

Bohr’s Atomic Model

Nucleus in center (protons and neutrons)

Electrons are in energy levels/energy shells surrounding the nucleus

Energy level 1 holds up to 2 electronsEnergy level 2 holds up to 8 electronsEnergy level 3 holds up to 18 electrons

Stability and Octet RuleAn atom is stable if its outer shell is full

OR has eight electrons (octet rule)

The outer shell is known as the VALENCE shell

The number of electrons in the valence shell determines the reactiveness of the the element

The closer to stable, the more reactive

If the shell is full, the atom is non-reactive

Noble gases

Let’s draw some atoms

*list the number of valence electrons for eachHydrogen

Helium

Oxygen

Neon

Magnesium

Unstable Atoms “like” to form bonds

to become stableIonic bonds

Covalent bonds

Warm Up 8/20Draw a fluorine atom

How many valence electrons does it have?What does that say about its reactivity?

Draw a fluorine ionHow many valence electrons does it have?What does that say about its reactivity?

Today 8/22Review ions

Atoms that have gained/lost electronsExample: sodium ion

Learn about ionic bondingExample: lithium chloride

Ionic BondsAttraction between oppositely charged ions

Covalent BondsSharing of valence electrons