Which two periods have the same number of elements

Why does argon exist in nature as individual argon atoms and chlorine exist in nature as 2 chlorine atoms covalently bonded together?

If 4.0 moles of X and 4.0 moles of Y react according to the hypothetical reaction below, how many moles of the excess reactant will be left over at the end of the reaction? 2X + 3Y yields X2Y3 1.3 mol Y left over 2.7 mol Y left over 1.

Consider the unbalanced equation for the decomposition of silver nitrate: AgNO3 (s) - - - >Ag (s) + NO2 (g) + O2 (g) 1. Write the balanced equation for the reaction. 2. When 54.0g of AgNO3 is heated, 4.60g of O2 is formed.

If prices rise and income stays the same, what is the effect on demand

Is evaporation exothermic or endothermic

Periodic table, chemistry questions who discovered lanthanides. how did they discover it, when did they discover it.

A flask containing 155cm^3 of hydrogen was collected under a pressure of 22.5kPa. What pressure would have been required in order for the volume of the gas to have been 90.0 cm^3 at constant temperature?

Which change is most likely to occur when a molecule of H2 and a molecule of I2 collide with proper orientation and sufficient energy? 1. a chemical change, because a compound is formed 2. a chemical change, because an element is formed 3.

Which substance is a diatomic molecule? a. he b. o2 c. co2 d. h2o?

What is the difference between the electronegativity values of sodium and bromine?