Chapter 2.1-2.3

The chemical basis of life: atoms, molecules, and water

What is all matter composed of?

atoms

what are atoms composed of?

subatomic particles

what is the simplest atom?

hydrogen

what are the 3 subatomic particles?

Protons(p^+), electrons(e^-), and neutrons(n^0)

what kind of charge does a proton have?

positive

where is a proton found?

inside the nucleus of an atom

how do you determine the number of protons in an atom?

the atomic number

what kind of charge does a neutron have and where is it found in an atom?

It is uncharged and in the nucleus

what kind of charge does an electron have and where is it found?

negative charge and in the orbitals around the atomic nucleus

in most atoms what is identical?

the number of protons and electrons

What is an orbital?

The region surrounding the nucleus of an atom where the chances of finding an electron

what is a spherical orbital called?

s orbitals

what is a propeller or dumbbell shaped orbital called?

p orbitals

what is the max number of electrons the first orbital can contain?

2

where are orbitals found?

electron shells or energy levels

what can energy be defined as?

the capacity to do work or cause a change

what kind of energy do electrons have?

kinetic energy

what direction do the 2 electrons in the innermost s orbital (1s) move?

opposite directions

what is the 2nd electron shell composed of?

one spherical s orbital (2s) and three dumbbell- shaped p orbitals (2p)

what can the second shell hold?

four pairs of electrons/ eight electrons

what does the shell closest to the nucleus fill up with?

the lowest energy electrons first, then each subsequent shell fills with higher energy electrons (one shell at a time)

what do unfilled electron shells tend to do?

share, release, or obtain electrons to fill their outer shell

what are the electrons in the outermost shell called

valence electrons

what do valence electrons allow for?

atoms to form chemical bonds with each other

what distinguishes elements from other elements?

the number of protons in its nucleus

what represents the number of protons and electrons in an atom?

atomic number

if magnesium has an atomic number of 12 how many protons does it have?

12

what results when the atomic number is equal to both electrons and protons?

net electric charge of zero

what do the rows/ periods of the periodic table indicate?

number of electron shells

what do the columns/ groups of the periodic table indicate?

indicate the numbers of electrons in the outer shell

how is atomic mass measured?

units of Daltons (Da)/ atomic mass unit (amu)

what does one dalton equal?

1/12 the mass of a carbon atom or about the mass of a proton or hydrogen atom

what is the atomic mass of a carbon atom?

12 Da

If hydrogen atoms have a smaller mass than carbon atoms, which contains more atoms in 1g?

hydrogen

what is a mole (mol)

any substance contains the same number or particles as there are in grams

ex. 12g of carbon = 1 mol of carbon

What was described by Amedeo Avogadro?

1 mole of any element contains the same number of atoms

what number is known as Avogardo’s number?

6.022 × 10²³

what is an isotope?

A form of an element that contains a different number of neutrons from the element’s other isotopes.

what does this mean 12^C

the most abundant form of the carbon atom

what does the purest form of carbon contain?

6p, 6n, an atomic # of 6 and an atomic mass of 12 Da

which isotopes are unstable?

the ones in nature

How is the length of time unstable isotopes persist measured?

in half lives

what is a half life?

is the time it takes for 50% of an isotope to decay

what are unstable isotopes called?

radioisotopes

why are radioisotopes special?

emit energy in the form of radiation as they decay and dont exist for long periods of time

what 4 elements account for the vast majority of atoms in living organisms?

oxygen, carbon, nitrogen, hydrogen

what percent do these organisms take up in a living organisms mass?

95%

what form do much of hydrogen and oxygen occur in in the body?

water (accounts for 60% of the mass of animals and 95% in plants)

why is nitrogen essential in the body?

vital in all proteins and nucleic acids

what element accounts for about 63% of the atoms in the body?

hydrogen

why does hydrogen only make up a small percentage of mass of the human body?

atomic mass of hydogen is so much smaller than that of heavier elements such as oxygen

what are mineral elements?

a chemical element other than the core 4 that is required for life

what percent of mineral elements make up the total mass of living organisms

less than 1%

what are important constituents of skeletons and shells of animals

calcium and phosphorus

what elements are key regulators of water movement and of electric currents that occur across the surfaces of many cells?

potassium and sodium

what are trace elements

element essential for normal growth and function of living organisms (only required in extremely small quantities)

what are examples of trace elements

iron and copper

what are two or more atoms bonded together called

molecule or a compound

ex. 2 oxygen molecules = O2

what is an emergent property

the properties of a compound differ greatly from those of its elements

how are atoms in molecules held together

chemical bonds

what is a covalent bond?

chemical bond where two atoms share a pair of electrons

when can covalent bonds occur

between atoms whose outer shells aren not full

what allows for atoms to be the most stable

when their outer shells are filled with electrons

what is a structural formula

Chemical formula for molecules in which each covalent valence is rep by a line indicating a pair of shared electrons

what is a double bond

occurs when the atoms of a molecule share two pairs of electrons (4 electrons)

what kind of bond is formed between an oxygen molecule (O2)

double bond

what can cause a covalent bond to be either polar or nonpolar

electronegativity

what does an atom’s electronegativity determine

is a measure of an atoms ability to attract electrons in a bond with another atom

what does it mean if an atom has a high electronegativity

attract more electrons more strongly (vice versa with lower EN)