AA Unit 3 Remediation

Which of the following best explains why Mendeleev's periodic table was organized according to atomic mass rather than atomic number, like modern periodic tables?

• atomic number was not discovered yet

• atoimc mass is unaffected by chemical reactions

• atomic number is more closely related to reactivity

• atomic mass varies among the isotopes of an element

Which element is described below?

malleable, soft, reacts explosively with water, displays a yellow flame went ignighted.

• sodium

• chromium

• lead

• strontium

Which element is described below?

Reacts with group 1 to make salts, low conductivity, gas/liquid states at room temperature

• potassium

• bromine

• phosphorus

• iron

What is the average atomic mass of Bearion, if 90% is Bearion-12 and 10% is Bearion-14?

What is the average atomic mass:

30% = 42

55% = 41

15% = 40

• 41.15amu

• 123amu

• 45 amu

• 41.5amu

The ionization of Calcium is higher than...

• magnesium

• beryllium

• aluminum

• barium

What is the average atomic mass: Lead-204 (23.5%), Lead-207 (24.1%), and Lead-208 ( ?? %)

**find missing % first by subtracting the other %s from 100.**

Round to the nearest tenth.

Why does fluorine have a higher electronegativity than astatine?

• fluorine has less energy levels, making the e- closer to the nucleus and harder to steal

• fluorine has more energy levels, making the e- harder to steal

• fluorine is smaller

• fluorine has 17 valence electrons

Li has an ionization energy of 520 kJ/mol. F has an ionization energy of 1680 kJ/mol. Which of the following is a possible explanation for the trend?

• Fluorine has strong attractive forces between the nucleus and the electrons. It takes more energy to remove an electron from fluorine than lithium.

• Each electron on an atom has a set amount of energy. Since fluorine has more electrons, then it will have more ionization energy than lithium

• Lithium has a smaller atomic radius than fluorine. It takes less energy for an electron to be added to the outer energy level on lithium than the outer energy level on fluorine.

• Ionization energy increases down the periodic table and decreases across the periodic table.

Which of the following is NOT a postulate in Dalton's atomic theory?

 I. Electrons follow specific paths around the nucleus.
 II. Atoms of the same element are identical in mass and properties.
 III. Atoms of one element are never changed into atoms of a different element.
 IV. Compounds are formed by a combination of two or more different kinds of atoms.

• i

• ii

• iii

• iv