Three science questions help please!

Which of the following is the best definition of an element?

Ostrovityanka [42]

Answer:

A. chemical substance whose atoms all have the same number of protons

Explanation:

An element is a substance which contains identical atoms that have the same number of protons in the nucleus.

Elements are arranged in the periodic table according to their atomic number (= number of protons): so atoms of different elements have a different number of protons in their nuclei.

For a neutral atom, the number of electrons around the nucleus is also equal to the number of protons.

Moreover, atoms of the same element can have a different number of neutrons, despite having the same number of protons - these atoms are called isotopes.

8 0

2 years ago

ANSWERRR PLEASEEEE!!!

GuDViN [60]

Answer:

50N to the left

Explanation:

I'll explain if you ask

6 0

2 years ago

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How does the currently accepted model of the nucleus provide evidence of the existence of the strong nuclear force?

olganol [36]

Answer:

Protons and neutrons are all attracted to each other as a result - the strong nuclear force. This is an attractive force that only has an effect over a very short range in the nucleus.

4 0

2 years ago

Which of the following statements are true? Check all that apply. Check all that apply. The gravitational force between two obje

AveGali [126]

The gravitational force between two objects is inversely proportional to the square of the distance between the two objects.

The gravitational force between two objects is proportional to the product of the masses of the two objects.

The gravitational force between two objects is proportional to the square of the distance between the two objects. no

The gravitational force between two objects is inversely proportional to the distance between the two objects. no

The gravitational force between two objects is proportional to the distance between the two objects. no

The gravitational force between two objects is inversely proportional to the product of the masses of the two objects. no

3 0

2 years ago

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When light of wavelength 240 nm falls on a cobalt surface, electrons having a maximum kinetic energy of 0.17 eV are emitted. Fin

dusya [7]

Answer:

(a) 5.04 eV (B) 248.14 nm (c) $1.21\times 10^{15}Hz$

Explanation:

We have given Wavelength of the light \lambda = 240 nm

According to plank's rule ,energy of light

$E = h\nu = \frac{hc}{}\lambda$

$E = h\nu = \frac{6.67\times 10^{-34} J.s\times 3\times 10^{8}m/s}{ 240\times 10^{-9} m\times 1.6\times 10^{-19}J/eV}= 5.21 eV$

Maximum KE of emitted electron i= 0.17 eV

Part( A) Using Einstien's equation

$E = KE_{max}+\Phi _{0}$ , here $\Phi _0$ is work function.

$\Phi _{0}=E - KE_{max}$ = 5.21 eV-0.17 eV = 5.04 eV

Part( B) We have to find cutoff wavelength

$\Phi _{0} = \frac{hc}{\lambda_{cuttoff}}$

$\lambda_{cuttoff}= \frac{hc}{\Phi _{0} }$

$\lambda_{cuttoff}= \frac{6.67\times 10^{-34} J.s\times 3\times 10^{8}m/s}{5.04 eV\times 1.6\times 10^{-19}J/eV }=248.14 nm$

Part (C) In this part we have to find the cutoff frequency

$\nu = \frac{c}{\lambda_{cuttoff}}= \frac{3\times 10^{8}m/s}{248.14 \times 10^{-19} m }= 1.21\times 10^{15} Hz$

5 0

2 years ago