Which of these electron transitions correspond to absorption of energy and which to emission?

n = 2 to n = 4,

Cobalt-60 is a radioactive isotope used to treat cancers. A gamma ray emitted by this isotope has an energy of 1.33 MeV (million electron volts; 1 eV = $1.602 \times 10 ? 19 \mathrm { J }$). What is the frequency (in Hz) and the wavelength (in m ) of this gamma ray?

Police often monitor traffic with "K-band" radar guns, which operate in the microwave region at 22.235 GHz ( 1 GHz = 109 Hz ). Find the wavelength (in nm and $\dot { \mathrm { A } } )$ of this radiation.

Write the full ground-state electron configuration for each:

S,

Kr

Graph the functions f(x) = 3/(x - 1) and g(x) = 2/(x + 1) together to identify the values of x for which $\frac{3}{x-1}<\frac{2}{x+1}.$

If f(x) = x - 1 and g(x) = 1/(x + 1), find the following. f(g(1/2))

Write each number in standard notation.

$$6.41 \times 10 ^ { 3 }$$

_

Rewrite the condition in Section 3.4 to use < operators instead of >= operators. What is the impact on the order of the comparisons?

Write a program that plays tic-tac-toe. The tic-tac-toe game is played on a $3 \times 3$ grid as in the photo at right. The game is played by two players, who take turns. The first player marks moves with a circle, the second with a cross. The player who has formed a horizontal, vertical, or diagonal sequence of three marks wins. Your program should draw the game board, ask the user for the coordinates of the next mark, change the players after every successful move, and pronounce the winner.

Antes, tú vivías en el centro de la ciudad, pero el mes pasado te compraste una casa en las afueras. Completa las oraciones usando el pretérito y el imperfecto.

(poder) Antes, no ________ dormir porque mi calle era ruidosa. Ayer, ________ dormir todo lo que quise.

A long, straight wire carries a current of 8.60 A. An electron is traveling in the vicinity of the wire. At the instant when the electron is 4.50 cm from the wire and traveling at a speed of $6.00 \times 10^{4} \mathrm{m} / \mathrm{s}$ directly toward the wire, what are the magnitude and direction (relative to the direction of the current) of the force that the magnetic field of the current exerts on the electron?

In this assignment, you will model the game of Bulgarian Solitaire. The game starts with 45 cards. (They need not be playing cards. Unmarked index cards work just as well.) Randomly divide them into some number of piles of random size. For example, you might start with piles of size 20, 5, 1, 9, and 10. In each round, you take one card from each pile, forming a new pile with these cards. For example, the sample starting configuration would be transformed into piles of size 19, 4, 8, 9, and 5. The solitaire is over when the piles have size 1, 2, 3, 4, 5, 6, 7, 8, and 9, in some order. (It can be shown that you always end up with such a configuration.) In your program, produce a random starting configuration and print it. Then keep applying the solitaire step and print the result. Stop when the solitaire final configuration is reached.

If $\lim _{x \rightarrow 0^{+}} f(x)=A$ and $\lim _{x \rightarrow 0^{-}} f(x)=B,$

$$\lim _{x \rightarrow 0^{+}} f\left(x^{2}-x^{4}\right)$$

Completa las oraciones usando el pluscuamperfecto.

Por fin, anunció que el experimento ________ (ser) un éxito.