Chemical Context Of Life (2) Flashcards
Organisms are composed of _____
Matter
Define matter
Anything that takes up space and has mass
Made up of elements
An element is
substance that cannot be broken down to other substances by chemical reactions
A compound is
A substance consisting of two or more elements in a fixed ratio
Emergent properties
Properties that emerge from the combination of compounds
Essential elements
About 20-25% of the 92 natural elements are required for life
Which elements make up 96% of living matter
Carbon, hydrogen, oxygen, and nitrogen
Trace elements
Are required by an organism in only minute quantities
Vertebrates require the element ______ for normal activity of _______
Iodine (I)
The thyroid gland
Which elements are 96.3% of human body mass (including water) - DONT NEED TO MEMORIZE
Oxygen
Carbon
Hydrogen
Nitrogen
Which elements make up 3.7% of human body mass (including water) DONT NEED TO MEMORIZE
Calcium, phosphorus, potassium, sulfur, sodium, chlorine, magnesium
What is an atom
The smallest unit of matter that still rains the properties of an element
Neutrons
No electrical charge
Protons
Positive charge
Packed together to form a dense core at the atomic nucleus
Electrons
Negatively charged
Cloud of negative charge around the nucleus
Daltons
The unit of measurement for neutron mass and proton mass - which are almost identical
Do we include electrons in the total atomic mass
No, because they’re so small that they can be ignored
An element’s atomic number is
The number of protons in its nucleus
Unless otherwise indicated, atoms have ______ number side protons and electrons
Equal
Mass number
The total sum of protons plus neutrons in the nucleus
Atomic mass
The atoms total mass can be approximated by the mass number
Find neutrons with
Mass number minus atomic number
Isotopes
Are two atoms of an element that differ in the number of neutrons
Radioactive isotopes
Decay spontaneously, giving off particles and energy
Too many or too few neutrons can make an element unstable
Energy
The capacity to cause change
Potential energy
The energy that matter possesses because of its location or structure
The electrons of an atom differ in their amounts of potential energy based on
Their distance from the nucleus
The farther electrons are from the nucleus,
the more potential energy they have
Electrons shells
The different states of potential energy of the electrons if an atom
The first shell, closest to the nucleus, …
Has the lowest potential energy
Electrons in outer shells have
Higher potential energy
When an electron absorbs energy
It moves to a shell farther out from the nucleus
Valence electrons
Are those in the outermost shell
Mostly determines chemical behavior of an atom
No more than __ electrons can occupy a single orbit
2
Atoms with incomplete valence shells can
Share and transfer valence electrons with certain other atoms
Chemical bonds
Attraction between atoms that share or transfer valence electrons causing them to stay close together
covalent bonds
the sharing of a pair of valence electrons by two atoms
Molecule
consists of two or more atoms held together by covalent bonds
A single covalent bond is the sharing of__
one pair of valence electrons
A double covalent bond is the sharing of —
two pairs of valence electrons
an atom’s valence
the bonding Capacity of an atom
valence of hydrogen
1
valence of oxygen
2
valence of nitrogen
3
valence of carbon
4
electronegativity
an atom’s attraction for the elections in a covalent bond.
The more electronegative an atom is,
the more strongly it pulls shared elections toward itself
In a non polar covalent bond,
the atoms share the electron equally
In a polar covalent bond,
one atom is more electronegative, and the atoms do not share the electron equally
unequal sharing of elections causes
a partial positive or negative charge for each atom or molecule
ions
the resulting oppositely charged atoms/molecules when atoms strip elections from their bonding partners
cation
a positively charged ion
anion
a negatively charged ion
ionic bands
when anions and cations attract each other
salts
ionic compounds
compounds formed by ionic bonds
often found in nature as crystals
Most salts are ____ when dry, but ____ in the water
stable
dissociate quite easily
Most of thestrongest bonds in organisms are…
covalent bonds that forma cell’s molecules
Many large biological molecules are held in their functional form by
weak bonds
A hydrogen bond forms when
a hydrogen atom, which is covalently bonded to one electronegative atom, is also attracted to another electronegative atom
often oxygen or nitrogen in living cells
van der Waals interactions
attractions between molecules that are close together as a result of the charges caused by elections grouping together when unevenly distributed
Strong
A molecules shape is determined by
the positions of its atoms’ orbitals
Molecular shape determines how
biological molecules recognize & respond to one another
