How do you find the number of valence electrons in an element using the periodic table?

Asample of aluminum foil contains 8.60 × 1023 atoms. what is the mass of the foil?

What is a metal replacement reaction

The twister and runaway train are two coasters at the same amusement park. both coasters start at the same height. the coaster for the twister is twice the mass of the coaster for the runaway train. which roller coaster has greater gravitational potential energy at the start of the ride?