Chem Final Flashcards
(35 cards)
Mendeleev’s Periodic table
- published a table based on both properties and atomic weight
- he arranged them in vertical columns so similar properties are in the same row
-He knew that not all the elements were discovered yet, so he had question marks for 45, 68, and 70
Properties of Hydrogen
This element does not match the properties of any other group so it stands alone. It is placed above group 1 but is not part of that group. It is very reactive, colorless, odorless gas at room temperature.
Group 1 Alkali metals
Extremely reactive and are never found in nature in their pure form. Reactivity decreases as you go down a group. They are silver colored and shiny. Their density is extremely low so that they are soft enough to be cut with a knife.
Group 2 Alkaline metals
Slightly less reactive than alkali metals but still not found in pure state in nature. They are silver colored and more dense than alkali metals.
Groups 2-12 Transition metals
Have a moderate range of reactivity and a wide range of properties. In general, they are shiny and good conductors of heat and electricity. They also have higher densities and melting points than groups 1 & 2.
Group 17 Halogens
All nonmetals. Most reactive nonmetals. Reactivity decreases as you go down a group. Poor conductors of heat and electricity.
Group 18 Noble Gases
Unreactive nonmetals. All are colorless, odorless gases at room temperature. All have completely filled outer energy levels.
properties of a metal
-malleable
-ductile
-tenacious
-good conductors
-poor insulators
-as you go down, they become more reactive
properties of a nonmetal
-brittle as solids
-not malleable
-not tenacious
-not ductile
-good insulators
-poor conductors
-as you go down, they become less reactive
Atomic radii
one half the distance between the nuclei of identical atoms that are bonded together
Ionization energy
is the energy required to remove the first electron from a neutral atom,
Ionization is always endothermic. Always requires energy to remove an electron.
Electron Affinity
the energy change that occurs when a neutral atom acquires an electron (exo+endo)
measure of attraction between the incoming electron and the nucleus
the stronger the attraction, the more energy is released.
electronegativity
measure of the ability of an atom in a chemical compound to attract electrons
Atomic radii trend across period
electrons are added one at a time to the outer energy shell. Electrons within a shell cannot shield each other from the attraction to protons. Since the number of protons is also increasing, the Zeff increases across the period.
Ionization energy trend across period
the ionization energy generally increases going across a period because when crossing a period, more protons are being added to the nucleus of the atoms. This results in an increase in nuclear charge.
Electron affinity trend across period
across the table, affinity values increase. As more electrons are added, atoms are getting closer to the noble gas notation.
electronegativity trend across period
tend to increase going across the table. Reason: Zeff increases so pull on incoming electrons is greater.
Atomic radii trend going down a group
the number of electrons and filled elecron shells increases, but the number of valence electrons remains the same. Electrons are found farther from the nucleus as the same number of filled energy shells increase.
Ionization energy trend going down a group
Ionization energy decreases going down a group. This is because the electron to be removed from the outer energy level is increasingly distant from the nucleus as a result of the atoms getting bigger.
Electron affinity trend going down a group
down the group, affinities become less (less energy is given off when the negative ions are formed).
electronegativity trend going down a group
tend to decrease going down a group. Electron shielding- increase the number of inner/shielding electrons as you move down groups. Exception is group 18. They do not tend to attract electrons as they have a filled outer shell.
Effective nuclear charge, Zeff
the actual nuclear charge a valence electron experiences. In a many-electron atom, the Zeff depends on 2 factors. 1. Attraction betwen electrons and nucleus. 2. Repulsion between electrons in orbitals.
Zeff= Z-S
Z: atomic number
S: screening constant, usually close to inner electrons
cation
a positive ion. It has lost electrons
anion
a negative ion. It has gained electrons
