Question

1. how many valence electrons does a group 1a metal atom have?

a. 1
b. 2
c. 3
d. 4

1. what would be the proper noble gas notation for oxygen?

a. ne2s²2p⁴
b. ne2s²2p¹
c. he2s²2p⁴
d. he2s²2p¹

1. given the above electron dot structure, what further information is required to find the identity of element x? x:

a. the number of valence electrons
b. the period in which the element is found.
c. the number of neutrons
d. the electric charge

1. what is the maximum number of electrons that can be present in each principal energy level of hydrogen?

a. n
b. n²
c. 2n
d. 2n²

1. what is the lowest energy state of an atom called?

a. the ground state.
b. the excited state
c. the solid state
d. the chaotic state

1. the concept that all moving particles have wave characteristics is attributed to ____________

a. de broglie
b. thomson
c. heisenberg
d. bohr

1. why must the photons wavelength increase after the collision?

a. the photon changes direction.
b. the photon changes speed.
c. the photon gives up some energy to the electron.
d. the photon starts spinning.

1. why are there dots beyond the \boundary\ of the atomic orbital?

a. the boundary encloses the volume in which the electron is found 90% of the time.
b. the boundary is three - dimensional, while the picture shows only two dimensions.
c. experimental error
d. the boundary encloses the volume in which the electron is found 50% of the time.

Explanation:

1. Group 1A elements have 1 valence electron.
2. Oxygen has 8 electrons. Helium (\(He\)) has 2 electrons. So, \(8 - 2=6\) electrons left. The electron configuration is \(1s^{2}2s^{2}2p^{4}\). In noble - gas notation (using \(He\) as the core), it is \([He]2s^{2}2p^{4}\).
3. Electron - dot structures show valence electrons. To identify an element, we also need to know the period (which gives the principal energy level, related to the number of electron shells).
4. The formula for the maximum number of electrons in a principal energy level \(n\) is \(2n^{2}\).
5. The lowest energy state of an atom is called the ground state.
6. The concept that all moving particles have wave characteristics is de Broglie's hypothesis.
7. When a photon collides with an electron, it gives up some energy to the electron. Using \(E = h

u=\frac{hc}{\lambda}\) (\(E\) is energy, \(h\) is Planck's constant, \(
u\) is frequency, \(c\) is the speed of light, \(\lambda\) is wavelength), a decrease in energy (\(E\)) leads to an increase in wavelength (\(\lambda\)).

1. The boundary of an atomic orbital encloses the volume where the electron is found 90% of the time. So, there can be dots (representing electron probability) outside the boundary.

Answer:

1. a. 1
2. c. \([He]2s^{2}2p^{4}\)
3. b. the period in which the element is found
4. d. \(2n^{2}\)
5. a. the ground state
6. a. de Broglie
7. c. The photon gives up some energy to the electron
8. a. the boundary encloses the volume in which the electron is found 90% of the time