Chpt. 6, The Periodic Table Flashcards
periodic table
a table of all known elements in which the elements are arranged according to trends in their properties
periodic law
the idea that the properties of elements repeat from time to time
main block elements
groups 1, 2, and 13-18
transition metals
groups 3-12
lanthanides
the top portion of the two rows over elements at the bottom of the periodic table
actinides
the bottom portion of the two rows of elements at the bottom of the periodic table
metals
the elements in the middle of the periodic table; these elements are shiny, good conductors, malleable, and ductile
nonmetals
any element that is not a metal; in terms of their properties, nonmetals vary greatly
metalloids
elements between the metals and nonmetals on the right portion of the periodic table; these elements have properties that are partially similar to metals, and partially to nonmetals
valence electrons
the outermost s and p electrons in an atom
periodic trends
the properties that change in a systematic way as one moves either across a row in the periodic table, or down a group
atomic radius
half the distance between two bonded atoms of the same element (because there is not an actual “radius” that physically exists); adding electrons to an atom generally increases the atomic radius
cations
ions with a positive charge
anions
ions with a negative charge
octet rule
atoms tend to gain or lose electrons so that they will have the same number of electrons as the nearest noble gas
things to consider:
- The nearest noble gas may be either before the element (just as neon is before aluminum) or after the element (as argon is after phosphorus)
- If the nearest noble gas is before the element of interest, the element will lose valence electrons until it has the same number of valence electrons as that noble gas. This will give it a positive charge. As a result, aluminum will lose three electrons to become like neon, giving it a +3 charge.
- If the nearest noble gas is after the element of interest, the element will gain valence electrons until it has the same number of valence electrons as that noble gas. This will give it a negative charge. As a result, phosphorus will gain three electrons to become like argon, giving it a -3 charge.
- Ignore the d- and f-blocks when counting forwards and backwards. In this way, gallium (Ga) wants to lose three electrons to become like argon – we just ignore all of the transition elements that are between them.
ionization energy
the amount of energy that is required to pull one electron off of an atom
shielding effect
electrons that are closer to the nucleus repel electrons that are farther from the nucleus away from themselves
periodic trends for ionization energy
As you move left to right across the periodic table, the ionization energies of elements increase. Consider this: Elements on the left side of the periodic table want to lose electrons because their nearest noble gases have fewer electrons than they do, so it doesn’t take much energy to make this happen. Elements on the right side of the periodic table want to gain electrons to be like the nearest noble gas, so it takes a lot of energy to pull off electrons.
As you move down a group, the ionization energies of elements decrease. This is due to the shielding effect. Because elements at the bottom of their periods have more energy levels, there are more electrons pushing on the outer electrons. This enhanced push makes it easier to pull off electrons (i.e. it takes less energy to pull an electron off).
multiple ionization energies
If you want to pull off more than one electron, more energy is required than to pull off just one. This is particularly true if you’re trying to pull electrons away from an element that has the same number of electrons as its nearest noble gas. For example, it takes only 522 kJ/mol of energy to remove one electron from lithium (which gives it the same number of electrons as helium), but 7,301 kJ/mol to remove a second (which takes it away from its happy helium configuration). Yet again, the octet rule is the cause of something amazing
electronegativity
The electronegativity of an element measures how hard it tries to pull electrons away from other atoms it is bonded to.
Elements on the right side of the periodic table really want to grab electrons.
Elements on the left side of the periodic table really want to lose electrons and have low electronegativities (i.e. they don’t want to gain electrons very much).
The noble gases, on the other hand, don’t really care about picking up electrons so have no noticeable electronegativities at all.
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