5.3 Flashcards
Why can’t scientists measure the diameter of a single atom?
Atoms have no well-defined border
What do you need to figure out the size of atoms?
Two atoms
Define atomic radius
Half the distance between the nuclei of two atoms when they are joined in a molecule
Atomic radius is measured in
Picometers
Molecules that can’t be single atoms will be found in
Diatomic molecules
Elements that are only found in diatomic molecules
Hydrogen Oxygen Nitrogen Fluorine Chlorine Bromine Iodine Everything except the first form a 7
Atomic radius ______ from top to bottom in a group
Increases
Atomic radius ______ from left to right across a period
Decreases
The difference in size as you go down a group is _______ than the difference as you go across a period
Greater
What are shielding electrons?
Inner core electrons
Atomic radius increases down a group because
The shielding effect of going down another energy level is greater than the effect of increasing protons
Atomic radius decreases across a period because
Within a period, shielding effect doesn’t change, so as the number of protons increases, the electrons are pulled closer and atomic size decreases
Ion
Atom or group of atoms that has a positive or negative charge, created by the transfer of electrons
Metallic elements _____ one or more electrons from highest energy level to make ______ charge ions
Lose
Positive
Cation
Ion with a positive charge
Decreases in size
Nonmetallic elements ____ one or more electrons to make _______ charge ions
Gain
Negative
Anion
Ion with a negative charge
Increases in size
Why do atoms form ions?
To become more stable like a noble gas
Ionization energy
Energy required to remove an electron from an atom to make a positive ion
Ionization energy _______ as you go down a group
Decreases
Ionization energy ______ from left to right across a period
Increases
1st ionization energy
Energy to remove first outermost electron
How can ionization energies be used to predict charges of cations?
Easy to remove first electron from group 1A metal atoms=little IE
Difficult to remove second electron=big IE
Group 1A metals tend to form cations with a 1+ charge because it wants to be like a noble gas
Why is first ionization energy of nonmetal much higher than alkali metal?
Number of protons increases while shielding stays constant, so it’s more difficult to remove an electron
Ionization energy decreases down a group because
Increases energy level= increases size=easier to remove an electron from atom so lower ionization energy
Ionization energy increases across a period because
Increases in protons/charge but no change in shielding means higher ionization energy
Metals lose electrons and ______ in size
Decrease
Nonmetals gain electrons and ______ in size
Increase
Size graph in a period
That backwards N shape from the worksheet First leg (low and decreasing) is cations Last leg (high and decreasing) is anions
Electronegativity
Ability of an atom to attract electrons when it’s bonded to another atom
Electronegativity ________ down a group because
Decreases because bigger atoms have a harder time attracting the outermost electrons
Electronegativity ________ across a period in
Increases
In representative elements
Metals have a ___ value of Electronegativity
Low
Nonmetals have a _____ value of Electronegativity except for
High except noble gases
