Chapter 2: The chemical foundation of life
An element is a substance that cannot be broken down by chemical reactions
Parts of an atom
o Neutrons (no charge)
o Protons (Positive charge)
o Electrons (negative charge)
Elements
Atomic number = the number of protons (also the number of electrons)
Atomic mass = Protons + neutrons
The number of protons determines unique chemical properties of an element
Electrons can be in different shells around the nucleus
o Shells are energy levels
o Electrons can store energy
o Outer shell holds the valence electrons
o Only 2 electrons on the inner shell
o Only 8 electrons in 2nd and 3rd shell
o 2 electrons per orbital
o 4 orbitals in 2nd and 3rd shells
o 1 electron goes in each orbital before they are paired up
What is a covalent bond?
o It is the sharing of a pair of electrons
What is an ionic bond?
o An electrostatic interaction
o The transfer of an electron
Why does ice float?
o There is less mass per unit of volume
o When water freezes, crystalline structure is formed with hydrogen bonds and leaves
gaps
How can insects walk on water?
o Cohesive properties and surface tension produced by hydrogen bonds
What is a solvent?
o It can dissolve solutes
o Water is the universal solvent
What is a solute?
o Something that dissolves in water
o An example is salt
Hydrophilic = dissolves in water
Hydrophobic = insoluble in water
How does water get up a tree?
o Capillary action/ evaporation
o Adhesion and cohesion
What is an acid?
An element is a substance that cannot be broken down by chemical reactions
Parts of an atom
o Neutrons (no charge)
o Protons (Positive charge)
o Electrons (negative charge)
Elements
Atomic number = the number of protons (also the number of electrons)
Atomic mass = Protons + neutrons
The number of protons determines unique chemical properties of an element
Electrons can be in different shells around the nucleus
o Shells are energy levels
o Electrons can store energy
o Outer shell holds the valence electrons
o Only 2 electrons on the inner shell
o Only 8 electrons in 2nd and 3rd shell
o 2 electrons per orbital
o 4 orbitals in 2nd and 3rd shells
o 1 electron goes in each orbital before they are paired up
What is a covalent bond?
o It is the sharing of a pair of electrons
What is an ionic bond?
o An electrostatic interaction
o The transfer of an electron
Why does ice float?
o There is less mass per unit of volume
o When water freezes, crystalline structure is formed with hydrogen bonds and leaves
gaps
How can insects walk on water?
o Cohesive properties and surface tension produced by hydrogen bonds
What is a solvent?
o It can dissolve solutes
o Water is the universal solvent
What is a solute?
o Something that dissolves in water
o An example is salt
Hydrophilic = dissolves in water
Hydrophobic = insoluble in water
How does water get up a tree?
o Capillary action/ evaporation
o Adhesion and cohesion
What is an acid?
