Chapter 2: Atoms & the Periodic Table

human body

4 nonmetals=oxygen, nitrogen, carbon, and hydrogen, comprise 96% of the mass of the human body -aka "building-block elements" -hydrogen and oxygen form water, the most prevalent substance in the body. -nitrogen, carbon, and hydrogen are found in the 4 main types of biological molecules--proteins, carbohydrates, lipids, and nucleic acids. proteins and nucleic acids contain nitrogen as well.

macronutrients (aka major minerals)

7 other elements also present in body (0.1-2% by mass): sodium(Na), potassium(K), chlorine(Cl), magnesium(Mg), sulfur(S), calcium(Ca), and phosphorus(P). -K, Na, and CL are present in body fluids. -Mg and S occur in proteins found in muscle. -Ca and P are present in teeth and bones. -P is also contained in nucleic acids, such as the DNA that transfers genetic information from one generation to another. -at least 100mg of each macronutrient is needed in the daily diet.

alkali metals

Group 1A; lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). -they share the following characteristics: 1. they are soft and shiny and have low melting points. 2. they are good conductors of heat and electricity. 3. they react readily with water to form basic solutions.

alkaline earth elements

Group 2A; beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). -are also shiny solids, but less reactive than the alkali metals.

halogens

Group 7A; group 17; fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and the rare radioactive element astanine (At). -in their elemental form, halogens contain 2 atoms joined together--F2, Cl2, Br2, I2. -fluorine and chlorine are gases at room temp. -bromine is a liquid. -iodine is a solid. -very reactive and combine with many other elements to form compounds.

noble gases

Group 8A; group 18; helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). -especially stable as atoms, so rarely combine with other elements to form compounds. -radon is a radioactive gas. -all of these elements have a completely filled outer shell of valence electrons; this electronic arrangement is especially stable, and as a result, these elements exist in nature as single atoms.

Rules to Determine the Ground State Electronic Configuration of an Atom

Rule 1: Electrons are placed in the lowest energy orbitals beginning with the 1s orbital. -in comparing similar types of orbitals from one shell to another (e.g., 1s and 2s), an orbital closer to the nucleus is lower in energy. Thus, the energy of a 1s orbital is lower than a 2s orbital. -within a shell, orbital energies increase in the following order: s,p, d, f. -these guidelines result in the following order of energies in the first three periods: 1s, 2s, 2p, 3s, 3p. Rule 2: Each orbital holds a maximum of 2 electrons.

group

a column in the periodic table; elements in the same group have similar electronic and chemical properties. -elements that comprise a particular group have similar chemical properties. -elements in the same group have the same # of valence electrons and similar electronic configurations. -the group #, using the 1A-8A system, equals the # of valence electrons for main group elements, except helium. -chemical properties of a group are similar because these elements contain the same electronic configuration of valence electrons.

element

a pure substance that cannot be broken down into simpler substances by a chemical reaction. -out of the 118 elements currently known, 90 are naturally occurring and 28 have been prepared by scientists in the laboratory. -each element is identified by a one- or two-letter symbol. -mixture of isotopes. - divided into 3 categories: main group elements, transition metals, and inner transition metals.

period

a row in the periodic table; elements in the same row are similar in size.

buckminsterfullerene

aka bucky ball; contains 60 carbon atoms joined together in a sphere of 20 hexagons and 12 pentagons in a pattern that resembles a soccer ball;

atoms

all matter is composed of the same building blocks called... -2 main components of an atom: nucleus and electron cloud.

isotopes

are atoms of the same element having a different # of neutrons. -generally, the chemical properties of isotopes are identical.

transition metal elements

are contained in the 10 short columns in the middle of the table.

metals

are shiny materials that are good conductors of heat and electricity. -all metals are solids at room temperature except for mercury, which is a liquid.

main group elements

consist of 2 columns on the far left and the 6 columns on the far right of the table. -none of these metals exist in nature as pure elements; rather, they are always combined with other elements to form compounds, such as, NaCl, sodium chloride.

inner transition metal elements

consist of the lanthanides and actinides, and they are not assigned group #s.

atomic mass unit

defines the mass of individual atoms relative to a standard mass. -1 amu = 1/12 the mass of a carbon atom that has 6 protons and 6 neutrons; 1 amu = 1.61x10^-24 g.

nonmetals

do not have a shiny appearance, and they are generally poor conductors of heat and electricity. -nonmetals like sulfur and carbon are solids at room temperature; bromine is a liquid; nitrogen, oxygen, and 9 other elements are gases.

periodic table

groups of elements that have similar properties arranged in a schematic way. -the elements in the periodic table are divided into 3 categories: metals, nonmetals, and metalloids. -arranged in order of increasing atomic # beginning at the upper left-hand corner. -valuable list of all known elements organized so that groups of elements with similar characteristics are arranged together. -arranged into 7 horizontal rows and 18 vertical columns. -the periodic table is organized into groups of elements with similar valence electronic configurations in the same column. -http://chemwiki.ucdavis.edu/@api/deki/files/30353/26dbac2e64570e0683190e1b66079cb3.jpg?revision=1

helium

has 2 electrons; electron configuration=1s^2.

carbon

has 3 elemental forms: diamond, graphite, and buckminsterfullerene; the 2 most common forms of carbon are diamond and graphite.

p orbital

has a dumbbell shape. Is higher in energy than an s orbital in the same shell because its electron density is farther from the nucleus.

s orbital

has a sphere shape of electron density. It is lower in energy than other orbitals in the same shell because electrons are kept closer together to the positively charged nucleus.

metalloids

have properties intermediate between metals and nonmetals. -only 7 elements are categorized as metalloids: boron(B), silicon(Si), germanium(Ge), arsenic(As), antimony(Sb), tellurium(Te), and astatine(At).

electronic configuration

how the electrons are arranged in an atom's orbitals. -shows what orbitals contain electrons and uses a superscript with each orbital to show how many electrons it contains. -the total # of electrons used for the electronic configuration of a neutral atom is always equal to the atomic #.

ball-and-stick representation

http://beyondpenguins.ehe.osu.edu/files/2011/06/web_water.jpg

nucleus

is a dense core that contains the protons and neutrons; most of the mass of an atom resides in the nucleus.

compound

is a pure substance formed by chemically combining two or more elements together.

orbital

is a region of space where the probability of finding an electron is high. Each orbital can hold 2 electrons. -the first energy orbital can hold 2 electrons. -the second energy level can hold 8 electrons. -the third energy level can hold 18 electrons.

graphite

is a slippery black substance used as a lubricant; contains parallel sheets of carbon atoms in flat 6-membered rings.

isotope symbol

is also written using the element symbol with the atomic # as a subscript and the mass # as a superscript. ^35_17 CL = Chlorine-35 https://d2jmvrsizmvf4x.cloudfront.net/0WDJbuFWRjG8vCSKnADA_3-isotope-notation-1.gif

electron cloud

is composed of electrons that move rapidly in the almost empty space surrounding the nucleus; comprises most of the volume of an atom.

diamond

is hard because it contains a dense 3-dimensional network of carbon atoms in 6-membered rings.

cation

is positively charged and has fewer electrons than the neutral atom.

ionization energy

is the energy needed to remove an electron from a neutral atom. -ionization energies decrease down a column of the periodic table as the valence electrons get farther from the positively charged nucleus. -ionization energies generally increase across a row of the periodic table as the # of protons in the nucleus increases.

mass number

is the sum of the # of protons and neutrons; symbolized by 'A'.

atomic weight/mass

is the weighted average of the mass of the naturally occurring isotopes of a particular element reported in atomic mass units.

periodic trends

many properties of atoms exhibit periodic trends; that is, they change in a regular way across a row or down a column of the periodic table. 2 properties that illustrate this phenomenon are atomic size and ionization energy.

trace elements (aka micronutrients)

required in the daily diet in small quantities, usually less than 15mg each. -iron for hemoglobin, the protein that carries oxygen on red blood cells, and myoglobin, the protein that stores oxygen in muscle. -zinc for the proper functioning of many enzymes in the liver and kidneys. -iodine for proper thyroid function. -although most of the trace elements are metals, nonmetals like fluorine and selenium are micronutrients as well.

principal energy levels (aka shells)

shells are numbered, n=1, 2, 3, 4, and so forth, beginning closest to the nucleus. -the farther an energy level is from the nucleus, the larger its volume becomes, and the more electrons it can hold. -consists of a set or orbitals, identified by s, p, d, and f.

radioactive

sometimes, one isotope of an element that emits particles or energy as some form of radiation.

hydrogen

symbol=H; Z=1; has one electron. -electron configuration=1s^1= 1s orbital contains 1 electron.

neon

symbol=Ne; Z=10; 10 electrons. -1s^2 2s^2 2p^6

electron

symbolized by 'e^-', has a negative charge. -1 charge; 9.1093x10^-28 -the mass of an electron is exceedingly far less than that of protons and neutrons. -the chemical properties of an element are determined by the # of electrons in an atom. -do not move freely in space; rather, they occupy specific energy levels. -electrons closer to the nucleus are held more tightly and are lower in energy. -electrons farther from the nucleus are held less tightly and are higher in energy.

neutron

symbolized by 'n', has no charge. 0 charge; 1.6749x10^-24

proton

symbolized by 'p', has a positive (+) charge. +1 charge; 1.6726x10^-24 -protons and neutrons have approx. the same mass. -opposite charges attract while like charges repel each other.

electron-dot symbol

the # of valence electrons around an atom often represented. -each dot represents 1 valence electron. -the dots are placed on the 4 sides of an element symbol. -for 1 to 4 valence electrons, single dots are used. With more than 4 electrons, the dots are paired. -the location of the dots around the symbol does not matter.

atom

the basic building block; Greek="unable to cut"

valence shell

the electrons in the outermost shell. -the chemical properties of an element depend on the most loosely held electrons, the valence electrons. -the period # tells the # of the valence shell. -Cl, chlorine, 1s^2 2s^2 2p^6 3s^2 3p^5, '3' is the valence shell, '2+5=7' are the valence electrons.

ground state

the lowest energy arrangement of electrons.

atomic number

the number of protons in the nucleus, symbolized by 'Z'. -tells us both the # of protons and electrons; # of protons = the # of electrons. -determines the identity of an element. -tells us how many electrons must be placed in orbitals.

atomic size

the size of an atom is measured by its atomic radius; that is, the distance from the nucleus to the outer edge of the valence shell. 2 periodic trends characterize the size of atoms. -the size of atoms increases down a column of the periodic table, as the valence electrons are farther from the nucleus. -the size of the atoms decreases across a row of the periodic table as the # of protons in the nucleus increases. An increasing # of protons pulls the electrons closer to the nucleus, so the atom gets smaller.

chemical formula

uses element symbols to show the identity of the elements forming a compound and subscripts to show the ratio of atoms(the building blocks of matter) contained in the compound.