How does the number of valence electrons for elements change across a period?

The number decreases.

The number increases.

The number stays constant.

The number increases and then decreases for noble gases

What is the coefficient in a chemical equation

Starting with 100 grams of uranium-238, after one half life has gone by, how many grams of uranium-238 will remain? A._12.5 grams B._25 grams C._50 grams D._100 grams

Which of the following statements is true? A) This reaction will be spontaneous only at high temperatures. B) This reaction will be spontaneous at all temperatures. C) This reaction will be nonspontaneous at all temperatures.

How many grams of magnesium would contain the same number of atoms as 26.982 grams of aluminum?

Density is the relation between the mass and volume of a body? True or false?

Name 3 characteristics that can be used to identify minerals

Hemoglobin, the oxygen-carrying protein in red blood cells, has four iron atoms per molecules ad contains 0.340 percent iron by mass. calculate the molar mass of hemoglobin

Nancy wants to find out how the steepness of a hill's slope affects the amount of soil that erodes from it. She has soil, a long pan, and a pile of books with which to build a model hillside. She has a watering can to model rainfall.

Elements on the periodic table are arranged by increasing?

What is the difference between molecular formula and molecular model