Which of these elements is a metal?

hafnium (Hf)

radon (Rn)

silicon (Si)

sulfur (S)

selenium (Se)

In which technique atomic absorption or atomic emission is flame temperature stability more critical?

A glass on a window sill contains 15.7 grams of cold water at 3.5°C. As it heats up in the sun, the water gains 570 joules of energy. The specific heat capacity of water is 4.186 joules/gram degree Celsius.

What do many scientists believe contributed to the extinction of the dinosaurs? Question 1 options: global warming plate tectonics predators asteroid impact

Upper C upper O subscript 2 (g) plus upper H subscript 2 (g) right arrow Upper C upper O (g) plus upper H subscript 2 upper O (l). What is being oxidized?

10. Hydrogen can exist as a liquid only at very low temperatures. This is primarily because the attractive forces between the molecules are A) van der Waals forces B) ionic bonds C) hydrogen bonds D) covalent forces

Why does the body of the bird covered with feathers?

One molecule of caffeine contains 8 atoms of carbon, 10 atoms of hydrogen, 2 atoms of oxygen, 4 atoms of nitrogen. write the formula for caffeine with the elements in the order they are given.

A piece of magnesium metal is heated in the presence of chlorine gas, and a reaction takes place. What compound will most likely be produced? A. Mg2C1 B. MgCl3 C. MgCl2 D. MgCI

What is the pressure of the gas in this mercury manometer if h = 81 mm and atmospheric pressure is 749 mmHg

A microscope containing two or more lenses is an