For elements 1-20, we can use the periodic table to predict.

A) An elements color

B) The number of valence electrons an element has

C) The number of isotopes an element has.

How well did tossing the pennies simulate half lives?

Radioactive isotope has a half-life of 1.2 billion years. as measured by the presence of the isotope and its stable decay product, a rock originally contained 10 grams of the radioactive isotope, and now contains 1.25 grams.

Why do some atoms gain electrons while others lose them in chemical reactions?

In this reaction, the covalent bonds in the molecules of hydrogen and oxygen are broken. Is the bond breaking process exothermic or endothermic? Explain your answer.

Both Democritus and Dalton suggested that matter is made up of atoms. true or false

Which of the following adaptations to life on land is found in both insects and modern reptiles? A. metamorphosis from a larval form B. body surfaces that resist evaporation C. tracheae to distribute oxygen D. ability to fly E.

Draw the correct structural formula for the following compounds: (be sure to include the hydrogen atoms where required) a) 2-pentene b) 2,3-diethyl-3,5-dimethylhexane c) 4-ethyl-2,6-dimethyl-2-heptene

Letters B and C on this model show us daytime on Earth. Both locations have daytime because of A) Earth's tilt on its axis. B) Earth's orbit around the sun. C) Earth's rotation on its axis. D) Earth's distance from the sun.

Blanking and Punching size:A compound die will be used to blank and punch a large washer out of 6061ST aluminum alloy sheet stock 3.80 mm thick. The outside diameter of the washer is 60.0 mm and the inside diameter is 28.0 mm.

Whats the difference between china and Europe