this is the periodic table entry for iron. the atomic number for iron is __? the number of electrons in a neutral iron atom is __?

The chart shows the bid provided by four contractors to complete a job. which contractor is the most cost-effective?

Which of the following is an example of physical change not a chemical change? a) a log gives off heat and light as it burns. b) a tree stores energy from the sun in its fruit. c) a penny lost in the grass slowly changes color. d) a water pipe freezes and cracks on a cold night.

Analyze the reaction to determine whether the reaction is exothermic or endothermic. explain your reasoning.