Lecture 4 Flashcards
1
Q
what are elements?
A
- can’t be broken down to other substances
- 92 naturally occuring, 114 named
2
Q
what are the essential elements?
A
- 25 of 92 essential for life
- macro elements (C,O,N,H) 96%
- micro elements (P, S, Na, K) 4%
- trace elements (required in minute quantities)
3
Q
what are trace element deficiencies?
A
- Iron (anemia/lighter leaves)
- iodine (lack of thyroid hormones)
4
Q
define some atomic structures
A
- atoms (smallest unit of matter that retains properties of the element)
- neutrons (no charge)
- protons (+ve charge)
- electrons (-ve charge)
- protons+neutrons from atomic nucleus
5
Q
what are isotopes?
A
- same number of protons, different number of neutrons
- radioactive (same chemical element, different mass with unstable nuclei; dissipate excess energy spontaniously by radiation)
6
Q
list bond strengths from most to least
A
- covalent
- ionic
- hydrogen
- van der waals interactions
7
Q
what is electronegativity?
A
- atom’s interactions for electrons in covalent bond
- stronger, more attractions
8
Q
what is a hydrogen bond?
A
- hydrogen atom covalently bonded to one electronegative atom; attracted to another electronegative atom
9
Q
what is molecular shape/function?
A
- determined by positions of atoms’ valence orbitals
- recognise/interact with each other with a specificity based on molecular shape
- similar shapes have similar biological effects
10
Q
what are chemical reactions?
A
- makr/break chemical bonds changing composition of matter
11
Q
what is important about carbon bonds?
A
- tetravalence (terahedron structure)
- flat shape
- vary in length
