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
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