Fig. 2.19
Photosynthesis
CHEMICAL REACTIONS
Making and breaking of chemical bonds
Sunlight powers the conversion of carbon dioxide and water to glucose and oxygen
- Reactants – Starting molecules
- Products – Final molecules
HYDROGEN BONDS
- Formed when a hydrogen atom covalently bonded to
one electronegative atom is also attracted to another electronegative atom
IONIC BONDS
Ion – A charged atom /molecule
- Cation – positively charged
- Anion – negatively charged
Ionic bond – Attraction between anion and cation
Ionic compounds (Salts) – Compounds formed by ionic bonds. Example: Sodium chloride
COVALENT BONDS
Chapter 2
The Chemical Context of Life
Covalent bond – Sharing of a pair of valence electrons by two atoms
- Non polar – atoms share electron equally
- Polar – atoms don’t share electron equally
Electronegativity – Atom’s attraction for electrons in a covalent bond
BONDS
96%
Carbon, hydrogen,
oxygen, and nitrogen
NATURAL
(92)
4%
Element
Calcium, phosphorus,
potassium, and sulfur
A substance that cannot be
broken down to other substances
by chemical reactions
TRACE
(needed in tiny amounts)
Compound
- Atomic number - Number of protons in an element’s nucleus
- Atomic mass - Sum of protons plus neutrons in element’s nucleus
- Isotopes - Different atomic forms of same element that differ in number of neutrons
A substance consisting of two or more elements in a fixed ratio
- Valence electrons - Electrons in outermost (valence) shell
- Elements with full valence shell are chemically inert
- Atoms with incomplete valence shells can
share or transfer valence electrons with other atoms
Fig. 2.3
SUBATOMIC PARTICLES
ATOM
- Neutrons (no electrical charge) - atomic nucleus
- Protons (positive charge) - atomic nucleus
- Electrons (negative charge) - form a cloud around nucleus
- Smallest unit of matter retaining properties
of an element
- Made of subatomic particles