BI 253 Chapter 2
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Anything that takes up space & has mass
What is an element?
Substance that can not be broken down to other substances by chem reactions
What 4 elements make up about 96% of human body weight?
Oxygen, Carbon, Nitrogen, Hydrogen
What % of body is composed of Oxygen?
What % of body is composed of Carbon?
What % of body is composed of Nitrogen?
What % of body is composed of Hydrogen?
What 7 elements make up approx 4% of body weight?
Calcium, Phosphorus, Potassium, Sulfur, Sodium, Chloride, Magnesium
What elements are found in the body in trace amts (<0.01%)
What is a molecule?
A combination of atoms of the same or different elements
Define a compound.
Molecule of different elements mixed in different ratios
An atom is . . . .
The smallest unit of all physical matter.
What is a proton, where is it located & what is its mass?
Positively charged particle in the nucleus w/ a mass of 1
What is a neutron, where is it located & what is its mass?
A particle w/ no charge, located in nucleus w/a mass of 1
What is an electron, where is it located & what is its mass?
Negatively charged particle that surrounds nucleus & has negligible mass
What is the atomic #?
# that defines the # of protons in an element
What comprises the atomic mass?
The # of protons & neutrons
Explain a chemical symbol.
1 or 2 letter shorthand for the name of the element
What are isotopes?
Atom w/ same # of protons as original but diff # of neutrons
Describe a radioisotope.
Unstable isotope that gives off energy in form of radiation.
What is an orbital?
Series or electron shells or energy levels around the nucleus.
What is the outermost electron shell called & what does it determine?
- Valence Shell
- Determines how the atom will react with other atoms
Explain the octet rule.
States that atoms w/ >3 electrons want to have 8 in their Valence Shell
A stable atom has ___ e‾ in its valence. These naturally occur in ___ ___.
An unstable atom has ____ e⁻ in its valence & wants to bond to form ____.
What 3 ways can atoms satisfy the octet rule?
- Gain e⁻ fr other atoms
- Lose e⁻ to other atoms
- Share e⁻ w/other atoms
Describe a non-polar covalent bond.
Shares e⁻ equally between atoms
Describe a polar covalent bond.
Shares e⁻ unequally & relies on electronegativity to stay together
What are 2 characteristics of Ionic Bonds?
- Complete transfer of e⁻
- Rely on electronegativity
Give 3 characteristics of a covalent bond.
- Strongest of all bonds
- Requires a lot of energy to break
- Very Stable
Attractive force an atom exerts on e⁻
What determines electronegativity?
# of p⁺ in an atom & distance of e⁻ fr nucleus
Describe an ionic bond.
e⁻ transferred fr 1 atom to another forming pos or neg ions which are attracted to each other
Positively charged ions are called ___.
Negatively charged ions are called ____.
What is a complex or polyatomic ion?
Grp of covalently bonded atoms that carry a charge
Oxidation is the. . . .
Loss of 1 or more electrons
Reduction is the . . . .
Gain of 1 or more electrons
LEO the lion says GER means what?
- Lose Electrons Oxidized
- Gain Electrons Reduced
Where does a hydrogen bond exist?
Between an electronegative atom & a hydrogen atom bonded to another electronegative atom
___ ___ ALWAYS involves a hydrogen atom
Hydrogen Bonds are stronger than ___ ___ but weaker than ___ & ___ bonds
- Van der Waals Forces
- Covalent & Ionic
Give 3 places were hydrogen bonds exist for our purposes.
- DNA base pairs
Explain Van der Waals Interactions.
Attractions between molecules that are close together as a result of hot spots of pos or neg charge
What are chemical reactions?
The making and breaking of chem bonds
What are reactants?
Raw materials or Ingredients in a chem reaction
What are products?
Finished product in a chem reaction
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