U1 C2: chemical context of life Flashcards
matter is
anything that takes up space and has mass
elements
substances that cannot be broken down to other substances by chemical reactions
compound
a substance made up of 2 or more elements in a ratio
compounds have different characteristics than their elements
emergent
how many elements are there
92
essential elements
20-25% of elements in the periodic table are needed for an organism to live
trace elements
elements required for living things in very small quantities
atom
smallest unit of an element still maintaining the original properties
protons
positively charged subatomic particle
electrons
negatively charged
neutrons
neutral
mass of an atom is measured in..
daltons or amu
neutrons and protons are
1 dalton/amu
atomic number
number of protons in the atom
- can also be the number of neutrons if the atom is neutrally charged
mass number
number of neutrons and protons
atomic mass
total mass of an atom
isotopes
atoms that have more NEUTRONS than others of the same element
all isotopes behave how in a chemical reaction?
similarly
orbitals
the 3-D space where a given electron spends 90& of its time
is it possible to know the exact location of an electron at a given moment?
nope
concentric-circle diagrams are…
2-D visualisations of atoms involving electrons orbiting the nucleus in concentric paths
what is the advantage of concentric-circle diagrams?
it’s convenient to work with and understand the chemistry of an atom, particularly involving its electrons
what is the disadvantage of concentric-circle diagrams?
concentric orbits only represent average distance between electron and nucleus; not representative of an atom’s actual structure
electron orbitals constitute …
shells
a single orbital can have how many electrons?
2 at most
s orbitals are…
spherical
p orbitals…
dumbell -shaped
first shell is comprised of …
1s (one s orbital)
second shell is comprised of …
2s (one s orbital), 2p (three p orbitals)
electrons in different orbitals share … but differ in …
the amount of energy (nearly) … move in different volumes of space
what causes the reactivity of a given atom?
the presence (or lack thereof) of one or more unpaired electrons in their orbitals
the electrons that tend to interact in atoms are the … such that the atom’s … are completed
unpaired electrons … valence shells
chemical bonds
the interactions between atoms with generally incomplete valence shells such that valence electrons are transferred or shared in order to complete valence shells
strong bonds
covalent bonds, ionic bonds (dry)
weak bonds
ionic bounds (aqueous, solutions), hydrogen bonds, van der waals interactions
covalent bonds
chemical bond that involved the sharing of a pair of valence electrons (unpaired valence electrons approach each other and form a shared covalent bond with each electron being attracted to the other atom’s nucleus)
