Chemistry Question...Please Help???i dont understand!?

Question

Which statement best compares the atomic radius of a potassium atom and the atomic radius of a calcium atom?

1)The radius of the potassium atom is larger because of its larger nuclear charge.

2)The radius of the potassium atom is larger because of its smaller nuclear charge.

3)The radius of the potassium atom is smaller because of its smaller nuclear charge.

4)The radius of the potassium atom is smaller because of its larger nuclear charge.

Answer 1

# 2 is correct.

As you go left to right across a period on the Periodic Table, you notice a trend that the atomic radii get smaller. This is because the electrons being added go into the same energy level-not a higher one that is farther from the nucleus. At the same time you are adding protons to the nucleus. As the number of protons in the nucleus increases, the attraction the electrons feel to those protons also increases. That means the electrons are pulled closer to the nucleus and the radii of the atoms get smaller.

This trend is only a general trend and there are exceptions, but we normally notice that group 2 atoms are smaller than the preceding group 1 atoms.

(by the way, the protons and electrons may be of different sizes, but they have the exact same strength charge-just opposite signs. Remember that mass of 1800 electrons = mass of 1 proton, but charge of 1 electron is 1- while charge of 1 proton is 1+ = equal but opposite charges)

Answer 2

2)The radius of the potassium atom is larger because of its smaller nuclear charge.

Answer 3

The periodic table is fascinating because it can be used to determine certain characteristics just by examining the period or group an element is in.

In this question, you are dealing with two elements that exist withing the same period. As you go across the group the number of protons (represented by the atomic number) increases. Naturally, the number of electrons increases as well to maintain a neutral charge. However, protons are much larger than electrons, and exert a much more powerful pull as they increase in number. This means that as you go towards the right of the period you would expect the radii to_____.

Answer 4

Try this--each question is a convert ## to &&. Think of it as a fraction of powers of 10. For instance, 17.2 s to ms is 17.2 x 10^0/10^–3 = 17.2 x 10^3. 2.56 mm to km would be 2.56 x 10^–3/10^3 = 2.56 x 10^–6. This method ALWAYS works for metric type conversions. It is not a dimensional analysis approach though. The last one is really convert 17.3 mL to L, because 1 cm3 = 1 mL so the problem is 17.3 mL to L! Hope this helps!

Answer 5

the answer is #4!