pg 29-57 Flashcards
4 elements common in all living organisms
O, C, H, N
element mass=
proteins plus neutrons
different forms of an element that have the same number of protons but a different number of neutrons.
isotopes
Some isotopes may emit neutrons, protons, and electrons, and attain a more stable atomic configuration (lower level of potential energy)
radioisotopes
chemical reactivity
the ability to combine and to chemically bond with each other.
two or more atoms chemically bonded together.
molecules
The Bohr model
-shows the atom as a central nucleus containing protons and neutrons, with the electrons in circular orbitals at specific distances from the nucleus
with the exception of the innermost shell, that atoms are more stable energetically when they have eight electrons in their valence shell
octet rule
another word for noble gases
inert
As a result of losing a negatively charged electron, they become positively charged ___
ions
since not all elements have enough electrons to fill their outermost shells, atoms form _____
chemical bonds
occur when two or more atoms bond together to form molecules or when bonded atoms break apart
Chemical reactions
Reversible reactions are those that can go in either direction. In reversible reactions, reactants turn into products, but when the product’s concentration goes beyond a certain threshold (characteristic of the particular reaction), some of these products convert back into reactants. At this point, product and reactant designations reverse. This back and forth continues until a certain relative balance between reactants and products occurs—a state called _____. A chemical equation with a double headed arrow pointing towards both the reactants and products often denote these reversible reaction situations.
equilibrium
- positive ions that form by losing electrons.
- Negative ions form by gaining electrons, which we call ____
- cations
- anions
We designate anions by their ____ ____ and change the ending to “___”,
- elemental name
- -ide
- thus the anion of chlorine is chloride, and the anion of sulfur is sulfide.
electron transfer
Scientists refer to this movement of electrons from one element to another
form between ions with opposite charges
ionic bonds
examples of electrolytes
sodium, potassium, and calcium
These bonds are stronger and much more common than ionic bonds in the molecules of living organisms
covalent bonds
two types of covalent bonds
polar and nonpolar
form between two atoms of the same element or between different elements that share electrons equally
nonpolar covalent bonds
Two weak bonds that occur frequently are ___ and ____. Without these two types of bonds, life as we know it would not exist.
-hydrogen bonds and van der Waals interactions
___ bonds provide many of the critical, life-sustaining properties of water and also stabilize the structures of proteins and DNA, the building block of cells.
Hydrogen
When polar covalent bonds containing hydrogen form, the hydrogen in that bond has a slightly ____ charge because hydrogen’s electron is…
- positive
- pulled more strongly toward the other element and away from the hydrogen
Hydrogen Bond
- common and occurs regularly between water molecules
- Individual hydrogen bonds are weak and easily broken; however, they occur in very large numbers in water and in organic polymers, creating a major force in combination
- Hydrogen bonds are also responsible for zipping together the DNA double helix
van der Waals interactions
- are weak attractions or interactions between molecules.
- can occur between any two or more molecules and are dependent on slight fluctuations of the electron densities, which are not always symmetrical around an atom
- For these attractions to happen, the molecules need to be very close to one another.
- These bonds—along with ionic, covalent, and hydrogen bonds—contribute to the proteins’ three-dimensional structure in our cells that is necessary for their proper function
As a result of water’s polarity, each water molecule attracts other water molecules because of the ____ charges between water molecules, forming hydrogen bonds. Water also attracts or is attracted to other
- opposite
- polar molecules and ions.
What makes ice less dense than liquid water.
Hydrogen bonding
What has the highest specific heat capacity of any liquids
water