U4L1 DE GP - Wed Dec 10 - 7.3 Size of atoms and ions pt1

​U4L1 - Wed Dec 10 - 7.3 Size of atoms and ions pt1

By Mikhail Kuchuk

If you had two quarters next to each other, one (weird) way to figure out their radius is by taking half the distance between the centers of the quarters

If the distance between the centers of two touching quarters is 1 inch..... then the radius of one quarter is half as much, 0.5 inches.

• The size of an individidual atom is hard to measure

• Instead scientists measure the distance between nuclei of atoms when theyre bonded to themselves and divide by 2 to get an atom's radius

• This is called the "bonding atomic radius", "atomic radius", or "covalent radius" or just "size"

Multiple Choice

The bonding atomic radius—also called the covalent radius or simply the "size" of an atom—is defined as:

• The total distance between two nuclei in a molecule

• Half the distance between two bonded nuclei in a molecule

• The radius of an atom when it is not bonded to anything

• The distance from the nucleus to the innermost electron

Multiple Choice

Which of the following correctly describes the bonding atomic radius?

• It is the same as the nonbonding (van der Waals) radius

• It equals the full distance between two bonded nuclei

• It is also called the covalent radius and refers to the "size" of an atom

• It can only be measured for noble gases

• The sizes of atoms are really small and is measured in angstroms (Å) or picometers (pm)

• 1 Å = 10^-10 m = 0.000 000 000 01 m

• 1 Å = 100 pm (1 pm = 10^-12 m)

• can be looked up on a chart (check your reference paper)

**a meter and a yard are about the same length***

Multiple Choice

What is the name of the unit of length equal to $$10^{-10}$$ m, or 100 picometers, commonly used to measure atomic size?

• Nanometer

• Angstrom

• Femtometer

• Micrometer

Multiple Choice

How many picometers (pm) are in one angstrom (Å)?

• 1 pm

• 10 pm

• 100 pm

• 1000 pm

Match

Match each element to its bonding atomic radius. Use the atomic radii chart.

• Fluorine

• Sulfur

• Bromine

0.72 Å

1..04 Å

1.14 Å

• 0.72 Å

• 1..04 Å

• 1.14 Å

Match

Match each element to its bonding atomic radius. Use the atomic radii chart.

• Oxygen

• Phosphorus

• Selenium

0.73 Å

1.10 Å

1.16 Å

• 0.73 Å

• 1.10 Å

• 1.16 Å

• Imagine that the distance between the center of two touching coins can be determined by adding together their radii

• Similarly you can predict the length of a bond between two atoms by adding their atomic radii

• Similarly you can predict the length of a bond between two atoms by adding their atomic radii

Multiple Choice

Use the atomic radii chart. Predict the bond length of an O–P bond.

• 0.66 Å

• 1.07 Å

• 1.73 Å

• 2.14 Å

Multiple Choice

Use the atomic radii chart. Predict the bond length of an S–Br bond.

• 0.99 Å

• 1.14 Å

• 2.13 Å

• 2.56 Å

• As you move right across a period, electrons are added to the same energy level, and protons are added to the nucleus.

• added protons make more positive charge that pulls more strongly on the electrons and makes the atoms smaller

• Going to the right generally makes atoms smaller

• As you move down a group, electrons are added to higher energy levels / shells. Atoms get bigger.

• Going down generally makes atoms bigger

• Atoms get bigger to the left across a period

• Atoms get bigger downward across a group

• Atoms get smaller to the right across a group and

• bigger down a period

• ***there are exceptions but I wont test you on them

Multiple Choice

As you move to the ________ across a period, the size of an atom generally decreases.

• left

• top

• bottom

• right

Multiple Choice

As you move to the ________ across a period, the size of an atom generally increases.

• right

• top

• bottom

• left

Multiple Choice

As you move ________ a group, the size of an atom generally increases.

• up

• left

• right

• down

Multiple Choice

As you move ________ a group, the size of an atom generally decreases.

• down

• left

• right

• up

Multiple Choice

Assuming they follow the general trend, which of the following correctly ranks Mg, Si, and Ar by increasing atomic radius?

• Mg < Si < Ar

• Si < Mg < Ar

• Ar < Si < Mg

• Mg < Ar < Si

Multiple Choice

Assuming they follow the general trend, which of the following correctly ranks Ca, Ga, and Kr by increasing atomic radius?

• Ca < Ga < Kr

• Ga < Ca < Kr

• Kr < Ga < Ca

• Ca < Kr < Ga

Multiple Choice

Assuming they follow the general trend, which of the following correctly ranks Li, Na, and K by increasing atomic radius?

• Li < Na < K

• K < Na < Li

• Na < Li < K

• K < Li < Na

Multiple Choice

Assuming they follow the general trend, which of the following correctly ranks C, Si, and Ge by increasing atomic radius?

• C < Si < Ge

• Ge < Si < C

• Si < C < Ge

• Ge < C < Si