Questions inside :) 5 problems :) double check my answers please? :)

Question

anonymous · Answer

#1: How are the elements arranged in the modern periodic table?

A.       by increasing atomic mass

 B.      by decreasing atomic mass

  C.     by increasing atomic number

   D,    by decreasing atomic number

***My answer: A.by increasing atomic mass

#2: Which of these sets of elements has similar properties?

    A.   hydrogen, helium, neon

     B.  oxygen, nitrogen, carbon

      C. strontium, magnesium, calcium, beryllium

      D. chromium, magnesium, iron, cobalt
**my answer: C

#3: Which element has properties most similar to sodium?

A.       potassium

B.       calcium

C.       aluminum

  D.     neon
***i think it is A. potassium..

or could it be B. calcium? idk :/

#4:  Why didn't Mendeleev include helium, neon, and argon in his periodic table?

A.       These elements did not fit in with his pattern.

 B.      These elements are gases and he didn't include gases.

 C.      The atoms of these elements had no atomic mass.

 D.      These elements had not yet been discovered.
***im not too sure on this one... i think it might be C.. but idk :/

#5: The periodic law describes trends seen across which of the following?
A.       the top half of periodic table

 B.      periods within the periodic table

  C.     radioactivity within the periodic table

   D.    elements with the same number of protons
**My answer: B. periods within the periodic table...

anonymous · Answer

im not too sure... do they look right to you?? please explain! thanks :)

preetha · Answer

How are the elements arranged in the modern periodic table?: By increasing atomic number, not mass.
Number 2 and 3 are right.  Check you book for the 4.

anonymous · Answer

for #1, ur sure its by increasing atomic NUMBER?

and i can't find anything about #4... help please??

and is #5 right?? :)

preetha · Answer

Yes. I am positive.  Please take a look at a periodic table before you do anything else.  Look at the way the numbers increase, one by one.  That is atomic number, number of protons.

preetha · Answer

And Mendeleve left out the noble gases because they had not been discovered yet.

anonymous · Answer

so these are my final correct answers?
1= C
2=C
3=A
4=D
5=B
?? is that right? :)