How many valence electrons would an element with atomic number 84 have

After an incandescent lamp is turned on, the temperature of its filament rapidly increases from room temperature to its operating temperature.

Describe the motion of the blocks before and after they are knocked down. Also describe the interactions of the blocks with other objects as they are knocked down and fall.

A maglev train requires which of the following? a. the track and the train must have the same mangetic poles b. the track and train must have different magnetic poles c.

A tungsten wire has resistance R at 20°C. A second tungsten wire at 20°C has twice the length and half the cross-sectional area of the first wire. In terms of R, the resistance of the second wire is (1) R/2 (2) 2R (3) R (4) 4R

Big Bertha tips the scales at 950 Newtons. What is her mass?

What does Kepler's second law state? A. Planets travel in ellipses. B. Planets sweep equal areas in equal times. C. A planet's apparent backward movement is termed retrograde motion. D.

Why do charges build up in a cloud

How does the wave model of electrons orbiting the nucleus account for discrete energy values?

An ecosystem is all the populations of organisms that live together and A. the microorganisms that depend on them. B. the organisms that generate energy from sunlight. C. the physical factors with which they interact. D.

Which statement about magnetic poles is accurate? A) Same magnetic poles attract, while different magnetic poles repel. B) Same magnetic poles attract, while different magnetic poles attract.