(Unit 1) Chapter 2: Chemical Context of Life Flashcards
Define:
Element
A substance that cannot be broken down to other substances by chemical reactions
Define:
Compound
A substance consisting of two or more different elements combined in a fixed ratio
Define:
Trace Elements
Elements required by an organism in only minute quantities
Name elements making up about 96% of human body weight (Element, Symbol, Atomic Number, Percentage of Human Body Weight) (4)
Oxygen (O, 8), 65.0%
Carbon (C, 6), 18.5%
Hydrogen (H, 1), 9.5%
Nitrogen (N, 7), 3.3%
Name elements making up about 4% of human body weight (Element, Symbol, Atomic Number, Percentage of Human Body Weight) (7)
Calcium (Ca, 20), 1.5% Phosphorus (P, 15), 1.0% Potassium (K, 19), 0.4% Sulfur (S, 16), 0.3% Sodium (Na, 11), 0.2% Chlorine (Cl, 17), 0.2% Magnesium (Mg, 12), 0.1%
Name elements making up less than 0.01% of human body weight (Element, Symbol, Atomic Number) (
Boron (B, 5) Chromium (Cr, 25) Cobalt (Co, 27) Copper (Cu, 29) Fluorine (F, 9) Iodine (I, 53) Iron (Fe, 26) Manganese (Mn, 25) Molybdenum (Mo, 42) Selenium (Se, 34) Silicon (Si, 14) Tin (Sn, 50) Vanadium (V, 23) Zinc (Zn, 30)
What is the smallest unit of matter that still retains the properties of an element?
Atom
Atoms are composed of even smaller parts called:
Subatomic particles
What three kinds of subatomic particles are relative in biology?
Neutrons, protons, and electrons
Protons and neutrons are packed together tightly in a dense core, or:
Atomic nucleus
True or False:
Protons and neutrons are very different in masses
False, neutrons and protons are almost identical in mass
How much do neutrons (and protons) weigh?
1.7 * 10^-24 gram
For atoms and subatomic particles (and molecules), what unit of measurement do we use?
Dalton
Who was the unit “dalton” named after?
John Dalton, the British scientist who helped develop atomic theory around 1800
The dalton is the same as the ______ ____ ____, or ___
Atomic mass unit
AMU
What is the mass of protons and neutrons?
Close to 1 dalton
True or False:
We can ignore electrons when computing the total mass of an atom
True, as the mass of the electron is just about 1/2000 that of a neutron or proton
Define:
Atomic number
The number of protons, which is unique to that element
Where is the atomic number written?
Written as a subscript to the left of the symbol of the element
Define:
Mass number
The sum of protons and neutrons in the nucleus of an atom
Where is the mass number written?
Written as a superscript to the left of an element symbol
Define:
Atomic mass
An approximation of the total mass of an atom
Define:
Isotopes
The different atomic forms of an element with different masses
Define:
Radioactive isotope
An isotope where the nucleus decays spontaneously, giving off particles and energy
Define:
Energy
The capacity to cause change - for instance, by doing work
Where are radioactive tracers used? (2)
Diagnostic tools in medicine (e.x. diagnosing kidney disorders)
Used in imaging (PET scanners etc.)
Define:
Potential energy
The energy that matter possesses because of its location or structure
An electron’s energy level is correlated with its average ________ from the _______
Distance
Nucleus
Electrons are found in different ________ ______, each with a characteristic average ________ and ______ level
Electron shells
Distance
Energy
The chemical behaviour of an atom is determined by what?
Distribution of electrons in the atom’s electron shells; Mostly on the number of electrons in its outermost shell
Define:
Valence electrons
Electrons in the outermost shell
Define:
Valence shell
The outermost electron shell
Define:
Inert
Chemically unreactive
Which three elements in the first 18 elements are said to be inert?
Helium
Neon
Argon
Define:
Orbital
The three-dimensional space where an electron is found 90% of the time
State the orbitals of the first electron shell
1 spherical s orbital (1s)
State the orbitals of the second electron shell
1 spherical s orbital (2s)
3 dumbbell-shaped p orbitals (2p)
No more than _ electrons can occupy a single orbital
2
True or False:
When atoms interact in a way that completes their valence cells, paired electrons are involved
False, unpaired electrons are involved
Define:
Chemical bonds
Attractions that hold atoms together when they share of transfer valence electrons
Define:
Covalent bonds
The sharing of a pair of valence electrons by two atoms
Two or more atoms held together by covalent bonds constitute what?
A molecule
In the formula H-H, what does the line represent?
A single (covalent) bond (a pair of shared electrons)
When the formula is written H : H, what type of diagram is this?
A Lewis Dot Diagram
What type of notation is H-H?
Structural Formula
What type of notation is H2?
Molecular Formula
With O2, two pairs of electrons are shared between the two oxygen atoms, what type of bond is that?
A double (covalent) bond
Define:
Valence
The bonding capacity of an atom
What does an atom’s valence usually equal?
Usually equals the number of unpaired electrons required to complete the atom’s outermost (valence) shell
Define:
Electronegativity
The attraction of a particular kind of atom for the electrons of a covalent bond (More electronegative = more strongly pulls shared electrons towards itself)
What is the difference between a nonpolar covalent bond and a polar covalent bond?
When electrons are shared equally (usually between two atoms of the same element), it is a nonpolar covalent bond
When one atom is more electronegative than the other, the electrons of the bond are not shared equally and it creates a polar covalent bond
Define:
Ionic bonds
The attraction between two atoms that are so unequal in electronegativity (more electronegative one strips electron away from the other, creating + and - attraction)
Define:
Ion
A charged atom or molecule
Define:
Cation
An ion with a positive charge
Define:
Anion
An ion with a negative charge
What are compounds formed by ionic bonds called?
Ionic compounds or Salts
Define:
Hydrogen bonds
Forms when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom
Define:
Van der Waals Interactions
Ever-changing regions of positive and negative charge that enable all atoms and molecules to stick to one another
Why do Van der Waals Interactions happen? When do they occur?
Electron are not always symmetrically distributed in a molecule and thus may accumulate by chance in one part of a molecule or another
Only occur when atoms and molecules are very close together
What are molecular shapes determined by?
Determined by the positions of the atoms’ orbitals (e.x. Water molecules are roughly V-shaped with two covalent bonds spread apart at 104.5 degrees)
Define:
Chemical reactions
The making and breaking of chemical bonds, leading to changes in the composition of matter
What are the starting materials in a chemical reaction called?
Reactants
What are the reactants in a chemical reaction converted to?
Products
Define:
Chemical equilibrium
The point at which the reactions offset one another exactly
