In general, as you move from right to left across a period, the number of valence electrons
a : increases
b : stays the same
c : increases and then decreases
d : decreases
i already tried increases and it's wrong

Scientists use laser range-finding to measure the distance to the moon with great accuracy. a brief laser pulse is fired at the moon, then the time interval is measured until the "echo" is seen by a telescope. a laser beam spreads out as it travels because it diffracts through a circular exit as it leaves the laser. in order for the reflected light to be bright enough to detect, the laser spot on the moon must be no more than 1.0 km in diameter. staying within this diameter is accomplished by using a special large-diameter laser. part a if λ = 540nm , what is the minimum diameter of the circular opening from which the laser beam emerges? the earth-moon distance is 384,000 km. express your answer to two significant figures and include the appropriate units.

When the magnetic domains in a material can be aligned, but eventually drift out of alignment, the material is

Ways that industry and agriculture use physical properties to separate substances