Which of these statements is incorrect regarding an atom of the element scandium?
a. its chemical symbol is sc.
b. it has 21 positively charged protons in its nucleus.
c. it has 21 negatively charged electrons.
d. it has 21 neutrons in its nucleus.

What is the temperature of one mole of helium gas at stp?

The lattice enthalpy (formation of ionic solid from ions in the gas phase) for agcl(s) is -916 kj/mol and the hydration enthalpy (dissolution of gaseous ions into water) is -850 kj/mol. how much heat (in joules) is involved in forming 1l of saturated agcl solution (1.8 × 10-4 g / 100 ml water) by dissolving agcl(s)? assume solution volume does not change much upon dissolution. the equations are given below. ag+(g) + cl−(g) æ agcl(s)

What is a number added in front of a formula in order to balance the equation