properties differ from those of individual elements
EX : table salt (NaCl)
A MOLECULE is the smallest unit of a compound that retains the chemical characteristics of the compound.
Composition of molecules is given by a MOLECULAR FORMULA
H 2 O C 8 H 10 N 4 O 2 - caffeine
ELEMENTS THAT EXIST AS DIATOMIC MOLECULES Remember: BrINClHOF These elements only exist as PAIRS. Note that when they combine to make compounds, they are no longer elements so they are no longer in pairs!
Neutrons: Mass Number minus the number of protons (mass number is protons and neutrons because the mass of electrons is negligible)
If it’s an atom, the protons and electrons must be the SAME so that it is has a net charge of zero (equal numbers of + and -)
If it does NOT have an equal number of electrons, it is not an atom, it is an ION. For each negative charge, add an extra electron. For each positive charge, subtract an electron (Don’t add a proton!!! That changes the element!)
The alkali metals, found in group 1 of the periodic table (formerly known as group IA), are very reactive metals that do not occur freely in nature. These metals have only one electron in their outer shell. Therefore, they are ready to lose that one electron in ionic bonding with other elements.
As with all metals, the alkali metals are malleable, ductile, and are good conductors of heat and electricity. The alkali metals are softer than most other metals.
Cesium and francium are the most reactive elements in this group. Alkali metals can explode if they are exposed to water.
The 38 elements in groups 3 through 12 of the periodic table are called "transition metals". As with all metals, the transition elements are both ductile and malleable, and conduct electricity and heat.
The interesting thing about transition metals is that their valence electrons, or the electrons they use to combine with other elements, are present in more than one shell. This is the reason why they often exhibit several common oxidation states.
There are three noteworthy elements in the transition metals family. These elements are iron, cobalt, and nickel, and they are the only elements known to produce a magnetic field.
The halogens are five non-metallic elements found in group 7 of the periodic table. The term "halogen" means "salt-former" and compounds containing halogens are called "salts". All halogens have 7 electrons in their outer shells, giving them an oxidation number of -1. The halogens exist, at room temperature, in all three states of matter:
Are completely nonreactive since they have eight valence electrons, making a stable octet.
Kr and Xe can be forced, in the laboratory, to give up some valence electrons to react with fluorine.
Since noble gases do not naturally bond to any other elements, one atom of noble gas is considered to be a molecule of noble gas. This is called a monatomic molecule. Ne represents an atom of Ne and a molecule of Ne.
The six noble gases are found in group 18 of the periodic table. These elements were considered to be inert gases until the 1960's, because their oxidation number of 0 prevents the noble gases from forming compounds readily.
All noble gases have the maximum number of electrons possible in their outer shell (2 for Helium, 8 for all others), making them stable.
An atom’s attraction to electrons in a chemical bond.
F has the highest, at 4.0
Fr has the lowest, at 0.7
If two atoms that are different in EN (END) from each other by 1.7 or more collide and bond (like a metal atom and a nonmetal atom), the one with the higher electronegativity will pull the valence electrons away from the atom with the lower electronegativity to form a (-) ion. The atom that was stripped of its valence electrons forms a (+) ion.
If the two atoms have an END of less than 1.7, they will share their unpaired valence electrons…covalent bond!
The energy required to remove the most loosely held valence electron from an atom in the gas phase.
High electronegativity means high ionization energy because if an atom is more attracted to electrons, it will take more energy to remove those electrons.
Metals have low ionization energy. They lose electrons easily to form (+) charged ions.
Nonmetals have high ionization energy but high electronegativity. They gain electrons easily to form (-) charged ions when reacted with metals, or share unpaired valence electrons with other nonmetal atoms.
Recent hurricanes and gasoline issues are proof of the existence of a new chemical element. Research has led to the discovery of the heaviest element yet known to science. The new element, Governmentium (Gv), has one neutron, 25 assistant neutrons, 88 deputy neutrons, and 198 assistant deputy neutrons, giving it an atomic mass of 312.
These 312 particles are held together by forces called morons, which are surrounded by vast quantities of lepton-like particles called peons. Since Governmentium has no electrons, it is inert; however, it can be detected, because it impedes every reaction with which it comes into contact.
A minute amount of Governmentium can cause a reaction that would normally take less than a second to take from four days to four years to complete. Governmentium has a normal half-life of 2- 6 years; It does not decay, but instead undergoes a reorganization in which a portion of the assistant neutrons and deputy neutrons exchange places. In fact, Governmentium's Mass will actually increase over time, since each reorganization will cause more morons to become neutrons, forming isodopes. This characteristic of moron promotion leads some scientists to believe that Governmentium is formed whenever morons reach a critical concentration. This hypothetical quantity is referred to as critical morass.
When catalyzed with money, Governmentium becomes Administratium, an element that radiates just as much energy as Governmentium since it has half as many peons but twice as many morons.