物理原子模型 DSE、CE 選擇題（第 3 頁）

21.

${}^{238}_{92}\mathrm{U}$ decays by emitting two $\alpha$ particles and two $\beta$ particles. Which of the following represents the resulting nuclide ?

22.

If the nucleus of an atom is represented by the symbol ${}^{214}_{83}\mathrm{X}$ , it means that this atom has

(1)

131

protons in its nucleus.

(2)

83

electrons outside its nucleus.

(3)

214

neutrons in its nucleus.

23.

The atomic number of Tin is $50$ and its mass number is $112$ . Which of the following is an isotope of Tin ?

24.

A U-235 nucleus would change to Ac-227 through a series of decay : ${}^{235}_{92}\mathrm{U}\xrightarrow{X}{}^{231}_{90}\mathrm{Th}\xrightarrow{Y}{}^{231}_{91}\mathrm{Pa}\xrightarrow{Z}{}^{227}_{89}\mathrm{Ac}$ What kind of particles are emitted at stages $X$ , $Y$ and $Z$ in the radioactive decay chain shown above ?

$X$	$Y$	$Z$
$\alpha$	$\alpha$	$\beta$
$\beta$	$\alpha$	$\beta$
$\beta$	$\beta$	$\alpha$
$\alpha$	$\beta$	$\alpha$

25.

During radioactive decay, ${}^{230}_{90}\mathrm{X}$ becomes ${}^{226}_{90}\mathrm{Y}$ . Which of the following statements would be correct ?

(1)The change would involve

\alpha

decay only.

(2)One

\alpha

particle and two

\beta

particles would be emitted.

(3)

X

and

Y

are two isotopes of the same element.

26.

An ancient piece of wood was tested for its age by carbon-14 dating method. The normal emission rate from $2$ g of carbon from a living plant is $20$ counts per minute. If the rate from $2$ g of carbon from the wood is $5$ counts per minute, and the half life of carbon-14 is $5700$ years, what is the approximate age of the wood in years ? (Background radiation may be neglected.)

27.

The atomic structure of isotopes of the same element differ from each other by having different numbers of

28.

Which of the following statements concerning isotopes of an element is/are correct ?

(1)They have the same number of neutrons.

(2)They have the same chemical and physical properties.

(3)They have the same atomic number but different mass numbers.

29.

Which of the following represents an alpha decay ?

(1)

{}^{238}_{92}\mathrm{U}\to{}^{234}_{90}\mathrm{Th}

(2)

{}^{215}_{85}\mathrm{At}\to{}^{211}_{83}\mathrm{Bi}

(3)

{}^{210}_{81}\mathrm{Tl}\to{}^{210}_{82}\mathrm{Pb}

30.

The two isotopes ${}^{35}_{17}\mathrm{Cl}$ and ${}^{37}_{17}\mathrm{Cl}$ of chlorine have different

(1)numbers of protons

(2)number of neutrons

(3)chemical properties