chem180: chapter 4; atoms and elements
Semiconductor
A compound or element exhibiting intermediate electrical conductivity that can be changed or controlled
Charge
A fundamental property of protons and electrons. Causes particles to experience forces such that like repel and unlike attract
Periodic law
A law that states when the elements are arranged in the order of increasing relative mass, certain sets of properties recur periodically
Anions
A negatively charged ion
Neutron
A nuclear particle with no electrical charge and nearly the same mass as a proton
Chemical symbol
A one- or two- letter abbreviation for an element, listed directly below the atomic number on the periodic table
Cation
A positively charged ion
Nuclear theory of the atom
A theory stating that most of the atom's mass and all of its positive charge are contained in a small, dense nucleus. Most of the volume of the atom is empty space occupied by negatively charged electrons
Silver
Ag
Aluminum
Al
Group (of elements)
Elements that have similar outer electron configurations and therefore similar properties. They occur in vertical columns on the periodic table
Nonmetals
Elements that tend to gain electrons in chemical reactions. They are found at the upper right side of the periodic table -not usually shiny, malleable, or ductile, and often poor conductors of heat and electricity; typically have low melting points and low densities elements: hydrogen (H), carbon (C), nitrogen (N), oxygen (O), chlorine (Cl), sulfar (S)
Metals
Elements that tend to lose electrons in chemical reactions; found at the left side and in the center of the periodic table -ductile, malleable, conductors of electricity, melted at <+ temps than nonmetals, solids at room temp, except Hg (mercury)
The macrominerals _____________________________________are involved in the formation of bones and teeth, and the maintenance of essential body functions.
Ca, P, K, Cl, S, Na, and Mg
Radioactive
Describes a substance that emits tiny, invisible, energetic particles from the nuclei of its component atoms
Dalton's Atomic Theory
(1) all matter is made up of tiny particles called atoms (2) all atoms of a given element are identical to one another and different from atoms of other elements (3) atoms of two or more different elements combine to form COMPOUNDS; a particular compound is always made up of the same kind of atoms and the same number of each kind of atom (4) a chemical reaction involves the rearrangement, separation, or combination of atoms; atoms are never created or destroyed in a chemical reaction
on the amu scale, the mass of a proton and a neutron have a mass of about
1 amu
mass of proton/neutron
1.673 x 10^-24 g
lanthanides/actinides (inner transition elements)
14 elements; part of periods 6 and 7, are placed at the bottom of periodic table
mass of electron
9.110 x 10^-28 g (less than proton/neutron)
Periodic table
An arrangement of the elements in which atomic number increases from left to right and elements with similar properties fall in columns called families or groups; created in 1872, Dmitri Mendeleev
Ion
An atom (or group of atoms) that has gained or lost one or more electrons, so that it has an electric charge
Gold
Au
Representative elements include
Group 1A (1), called Alkali metals Li, Na, K, Rb, Cs, and Fr Group 2A (2) called Alkaline earth metals Be, Mg, Ca, Sr, Ba, and Ra Groups 3A (13), 4A (14), 5A (15), and 6A (16) Group 7A (17), called Halogens F, Cl, Br, I, and At Group 8A (18), called Noble gases He, Ne, Ar, Kr, Xe, and Rn
Main-group elements
Groups 1A-8A (CAS System) on the periodic table. These groups have properties that tend to be predictable based on their position in the periodic table
period 1 contains two elements
H and He
atomic number examples
Hydrogen has atomic number 1; every H atom has 1 proton. Carbon has atomic number 6; every C atom has 6 protons. Copper has atomic number 29; every Cu atom has 29 protons. Gold has atomic number 79; every Au atom has 79 protons.
period 2 contains eight elements
Li, Be, B, C, N, O, F, He
period 3 contains eight elements
Na, Mg, Al, Si, P, S, Cl, Ar
Sulfur
S
Alkali metals; Group 1A
The Group 1A elements, which are highly reactive metals; soft shiny metals; good conductors of heat and electricity, and have relatively low melting points; react vigorously with water and form white products when they combine with oxygen elements: lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr)
Alkaline earth metals; Group 2A
The Group 2A elements; shiny metals like those of group 1A but not as reactive elements: beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra)
Halogens: Group 7A
The Group 7A elements, which are very reactive nonmetals (esp. fluorine and chlorine) and form compounds with most elements elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At)
Noble gases: Group 8A
The Group 8A elements, which are chemically unreactive; seldom found in combination with other elements elements: helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), radon (Rn);
Transition metals
The elements in the middle of the periodic table whose properties tend to be less predictable based simply on their position in the periodic table. They lose electrons in chemical reactions, but do not necessarily acquire noble gas configuration
Nuclear radiation
The energetic particles emitted from the nucleus of an atom when it is undergoing a nuclear process
Percent natural abundance
The percentage amount of each isotope of an element in a naturally occurring sample of the element
Atom
The smallest identifiable unit of an element; all elements listed on the pt are made up of atoms; building blocks of everything around us; too small to see with naked eye
Atomic mass unit (amu)
The unit commonly used to express the masses of protons, neutrons, and nuclei. 1 amu = 1.66 x 10^-24 g
Metalloids
Those elements that fall along the boundary between the metals and the nonmetals in the periodic table; their properties are intermediate between those of metals and those of nonmetals -better conductors of heat and electricity than nonmetals, but not as good as metals; are semiconductors because they can be modified to function as conductors or insulators elements: (B, Si, Ge, As, Sb, Te, Po, At)
electron
a negatively charged particle that occupies most of the atom's volume but contributes almost none of its mass; found to be much smaller than the atom and to have an extremely small mass
proton
a positively charged nuclear particle; found that atoms contained the + charged particles that were much heavier than electrons; its mass is approximately 1 amu
Match the elements to the description: A. Metals in Group 4A (14) (1) Sn, Pb (2) C, Si (3) C, Si, Ge, Sn B. Nonmetals in Group 5A (15) (1) As, Sb, Bi (2) N, P (3) N, P, As, Sb C. Metalloids in Group 4A (14) (1) C, Si, Ge (2) Si, Ge (3) Si, Ge, Sn, Pb
a. (1) Sn, Pb b. (2) N, P c. (2) Si, Ge
State the number of protons in each atom. A. A nitrogen atom (1) 5 protons (2) 7 protons (3) 14 protons B. A sulfur atom (1) 32 protons (2) 16 protons (3) 6 protons C. A barium atom (1) 137 protons (2) 81 protons (3) 56 protons
a. (2) 7 protons b. (2) 16 protons c. (3) 56 protons
An atom of zinc has a mass number of 65. A. How many protons are in the nucleus? (1) 30 (2) 35 (3) 65 B. How many neutrons are in the nucleus? (1) 30 (2) 35 (3) 65 C. What is the mass number of a zinc atom that has 37 neutrons? (1) 37 (2) 65 (3) 67
a. 30 b. 35 c. 67
An atom has 14 protons and 20 neutrons. A. Its atomic number is (1) 14 (2) 16 (3) 34 B. Its mass number is (1) 14 (2) 16 (3) 34 C. The element is (1) Si (2) Ca (3) Se
a. 34 b. 34 c. Si
Select the correct symbol for each element: A. Calcium (1) C (2) Ca (3) CA B. sulfur (1) S (2) Sl (3) Su C. iron (1) Ir (2) FE (3) Fe D. sodium (1) S (2) So (3) Na E. magnesium (1) Mg (2) Mn (3) Ma
a. Calcium Ca (2) b. Sulfur Su (3) c. Iron Fe (3) d. Sodium Na (3) e. Magnesium Mg (1)
Select the correct element name for each symbol: A. N (1) neon (2) nitrogen B. P (1) potassium (2) phosphorus C. Ag (1) silver (2) gold D. K (1) krypton (2) potassium E. F (1) fluorine (2) fempto
a. Nitrogen N(2) b. Potassium P (1) c. Silver Ag (1) d. Potassium K (2) e. Fluorine F (1)
Is each of the following statements true or false? A. The mass of an electron is greater than the mass of a proton. B. Protons have a positive charge, and electrons have a negative charge. C. The nucleus of an atom contains only the protons and neutrons.
a. false b. true c. true
periodic table; elements
are arranged according to similar properties in vertical columns called groups
chemical symbols
are one or two letter abbreviations for an element's name; when containing two letters, the second is not capitalized ex: Co = cobalt; CO = two elements, carbon and oxygen
Isotope
atoms with the same number of protons but different numbers of neutrons; atoms of the same elements that have different masses
malleable
can be hammered into a flat sheet
electrical charges in an atom
can be positive or negative when: -two POSITIVE charges REPEL each other <-----+ +-------> -two NEGATIVE charges REPEL each other <------- - - ------> -unlike charges ATTRACT each other ------> +- <-------- -------> -+ <---------
ductile
can be shaped into wires
Carbon (C): chemical link to industry
carbon atoms can arrange themselves in different ways to make different substances -graphite: used for lubricants and in pencils, contains carbon atoms connected to each other in planes of hexagonal rings -diamonds: transparent and much harder than graphite, carbon atoms are arranged in a rigid structure forming diamonds
group
each vertical column of the period table contains a group (family) of elements that have similar properties
Mass number (A)
for a single atom; the sum of the number of neutrons and protons in the nucleus of an atom mass number = # protons + # neutrons
transition elements
group numbers followed by the "B"
representative elements
groups 1A-8A
atom of any element is electrically neutral; it has a net charge of zero
has an equal number of protons and electrons; a neutral atom of calcium, atomic number 20, contains 20 protons and 20 electrons. It has zero net charge.
periods
horizontal rows of elements on the periodic table
Dalton's Atomic Theory; history
in 1808, the idea of atoms became scientific theory; John Dalton (1766-1844) developed an atomic theory proposing that atoms were responsible for the combinations of elements in compounds
Atom; discovery
in 1897, J. J. Thomson discovered that cathode rays were streams of small negatively charged particles called electrons; proposed the "plum pudding" model of an atom in which protons and electrons were distributed throughout the atom -J. J. Thomson's "plum pudding" model had protons and electrons scattered throughout the atom. -in 1911, Ernest Rutherford worked with J. J. Thomson and developed a new structure for the atom based on Rutherford's gold foil experiments; realized that atoms contain a nucleus and a region of space around the center of the atoms occupied electrons -in 1932, James Chadwick discovered that the nucleus of the atom contained neutral particles called neurons
group number
is written at the top of each vertical column (group) in the periodic table
the masses of protons and neutrons in the nucleus of an atom determine
its mass
mass of the atom
mass is due to the protons and neutrons in the nucleus; electrons have a much smaller mass
atom; strucutre
nucleus: small region in the center with positive charge; also contains neutral particles protons: positively charged particles electrons: negatively charged particles a region of space around the center of the atoms occupied by electrons
atomic number (Z)
of an element is equal to the number of protons in the nucleus of an atom of that element; whole number that appears above the symbol of element on pt atomic number = number of protons in atom
what four elements make up 96 % of our body mass
oxygen (O), carbon (C), hydrogen (H) and nitrogen (N) -only 20 elements are essential for the well-being and survival of the human body.
over the centuries, elements have been named for
planets, mythological figures, minerals, geographic locations, famous people
elements
pure substances from which everything else is built
atomic symbol
represents a particular isotope of an elements; gives the mass number in upper L corner and atomic number in lower L corner
nucleus
small core at the center of an atom containing most of the atom's mass and all of its positive charge. It is made up of protons and neutrons
subatomic particles
smaller bits of matter; proton, neutron, electron; discovered because of electrical charge -by the end of the 1880s, experiments with electricity showed that atoms were composed of tiny particles (subatomic particles) including protons, neutrons, and electrons; it was shown that some subatomic particles in an atom have CHARGE
Californium (Cf)
source of name: California
Chlorine (Cl)
source of name: Chloros "greenish-yellow (greek)
Iodine (I)
source of name: Ioeides "violet" (greek)
Curium (Cm)
source of name: Marie and Pierre Curie
Copernicium (Cn)
source of name: Nicolaus Copernicus
Magnesium (Mg)
source of name: magnesia, a mineral
uranium (U)
source of name: planet uranus
Titanium (Ti)
source of name: titans (mythology)
Atomic mass
unit (amu), defined as one-twelfth of the mass of the carbon atom with 6 protons and 6 neutrons; a weighted average of the masses of each naturally occurring isotope of an element; atomic mass of all elements in the pt is the average mass of the atoms in an element compared to the mass of the carbon atom (6 p, 6 n)
