Chapter 2: the chemical context of life Flashcards
Matter
Has mass
Occupies space
Elements
Building blocks of matter
Can not be chemically broken down into other substances
Compounds
Molecules containing atoms of 2 or more elements
Not all molecules are compounds but all compounds are molecules
Deoxyribonucleic Acid (DNA)
Transmits information across generations
Holds information for building RNA proteins
Sodium Metal, Chlorine Gas, Sodium Chloride
Highly reactive in water
Poison used in chemical warfare
Salt
Elements of life
25 of 92 natural elements are essential for humans and must. have to live and reproduce
Bulk elements need in large amounts
Trace elements need in small amounts
Atom
The smallest unit of matter that retains properties of that element
Subatomic Particles
Proton: +, Nucleus
Neutrons: Neutral, nucleus
Electron: - , Electron cloud
Protons and Nucleous
From nucleus
Central portion of atom
most of mass of atom
very small volume
Electrons
small, constantly moving
electron cloud around nucleus
most of volume of atom
Atomic Composition
Change # protons: Atom becomes new elements
Change # neutrons: Atoms becomes new isotope and remains same elements
Change # electrons: change charge and neutral becomes ion
Describing elements
Atomic Number: # of protons
mass number: # protons + neutrons for one atom
Atomic Mass: the average mass of all isotope of an element
Radioactivity
unstable isotopes decay, give off energy
carbon 14 to nitrogen 14
Neutral atoms vs ions
Balanced charge
Same # protons as electrons
Changing # electrons
Makes charged - ion
Cation - positively charged
Anion - negatively charged
Electrons
Most associated with chemical, bonding
orbitals hold electrons: max 2 electrons per orbital
orbitals into electron shells: 1st = 1 orbitals, 2nd = 4 orbitals, 3rd = 4 orbitals
outer - most occupied shell = valence shell
Unpaired electrons
Atoms most stable when valence shell ( VS ) is full ( or becomes empty)
Electronegativity
How strongly atoms attracts electrons
Covalent bonds
Sharing electrons: Fills valence shell of both atoms and both increased stability
Single, double, triple bonds possible
Ionic Bonds
Electrical attraction between action and anion
Large difference in electronegative
Atoms lose/gain electrons: forms ions
full valence shells for both
Electronegativity and bonds
Sharing electrons = covalent bonds
equal= non polar covalent bond
unequal= polar covalent bond
Losing/gaining = ionic bond
Polar Covalent bonds
Electron unequally shared
slight positive and slight negative
Hydrogen bonds
Slight + and - attract
polar molecule to polar molecule
Molecular shape
Determined by bonding
number of electrons pairs shared/atoms in molecule
central atom usually with space from 4 pair of valence electrons
Electrons repel each other
shared and unshared
negative repels negative
structure/function relationship
forms determines function
form determine by: bonds within molecule, hydrogen bonds, aspects of environment
