Is the following sentence true or false? Mendeleev used his periodic table to predict the properties of undiscovered elements.

Within nonmetals, ions that have more electrons tend to be bigger than ions that have fewer additional electrons why?

An electronic circuit element consists of 23 mg of silicon. An electric current through the circuit adds heat at a rate of 7.4 x 10-3 J/s.

How do the number of electrons in the second energy shell of an atom change going across period 2 in the periodic table? A. The number of electrons increases by 1, from left to right. B.

In a report to a supervisor, a chemist described an experiment in the following way: "0.0800 mol of H2O2 decomposed into 0.0800 mol of H2O and 0.0400 mol of O2.

1. Is O2 a compound? Explain. 2. Is O2 a molecule? Explain. 3. State the law of conservation of matter, and give an example demonstrating its meaning. 4. Electrolysis is used to break liquid water into hydrogen and oxygen gas.

Assume 3 molecules of Fe react according to the following equation. 3Fe + 4H2O Fe3O4 + 4H2 How many molecules of H2 are produced? How many water molecules are required? What is the mole ratio of Fe to H2O?

10.0 mL of a HF solution was titrated with a 0.120 N solution of KOH; 29.6 mL of KOH were required to completely neutralize the HF. Calculate the normality of the HF solution.

The number of grams present in 1.35 mol of Fe is

Which can associate a suspect's gun with a crime?

In which era did the first fish appear? a. Carboniferous b. Paleozoic C. Mesozoic d. Permian