The original amount of radioactive substance is 10 grams. After several years, 2.5 gtams of the substance is remaining. How many half-lives havr passed since the mass of the subtance was 10 grams?

Which of the following particles has almost no mass? proton neutron electron

How to calculate acceleration

Which is a cause of polarity in water molecules? partial negative charge on the hydrogen atoms partial positive charge on the oxygen atom high electronegativity difference between oxygen and hydrogen low electronegativity difference between oxygen

What type of contamination occurs if a paint chip falls into soup

Select the correct answer. What are the products of the acid-base reaction between HNO3 and NaOH?

Which are the hybrid orbitals of the carbon atoms in the following molecules? (a) H3C-CH3 sp sp2 sp3 (b) H3C-CH═CH2 sp sp2 sp3 (c) CH3-C≡C-CH2OH sp sp2 sp3 (d) CH3CH═O sp sp2 sp3

Which of the following pollutants is NOT created by fossil fuels? a. sulfur dioxide c. nitrogen dioxide b. phosphodioxide d. carbon dioxide

What causes velocity to change?

A radioactive sample is 555 years old. It's half life is 111 years. How many half lives?

An ion of magnesium has 12 protons and a charge of + 2. how many electrons are in this ion? A. 2 B. 20 C. 12 D. 14