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3 years ago

Question 19 of 25 The atomic number of the element radium is 88. How many neutrons does radium-226 have?

Chemistry

1 answer:

Mazyrski [523]3 years ago

4 0

Answer:

B. 138

Explanation:

Based on isotope notation:

$^X_nA$

For the atom A, the mass number, X, is the sum of neutrons and protons and

n is the number of protons = Atomic number.

The number of protons depends of the nature of the atom. For example, Carbon has 12 protons, hydrogen 1 and Radium has 88 protons.

The radium-226 means the mass number is 226. Thus, number of neutrons are:

Mass number - Atomic number

226 - 88 = 138

Right answer is:

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a sample of a substance has a density of 1.75 g/cm3 and a mass of 14.7 g. What volume does the sample occupy?

Zigmanuir [339]

The volume occupied by the sample is 8.4 cm³

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3 years ago

Write the quantities 3 × 10^-4 cm and 3 × 10^4 km in ordinary notation

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3 years ago

The planet Mercury takes 176 days to do one spin around its pole. Compared to the Earth,

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Answer:

The sun would appear to move more slowly across Mercury's sky.

Explanation:

This is because, the time it takes to do one spin or revolution on Mercury is 176 days (which is its period), whereas, the time it takes to do one spin or revolution on the Earth is 1 day.

Since the angular speed ω = 2π/T where T = period

So on Mercury, T' = 176days = 176 days × 24 hr/day × 60 min/hr × 60 s/min = ‭15,206,400‬ s

So, ω' = 2π/T'

= 2π/15,206,400‬ s

= 4.132 × 10⁻⁷ rad/s

So on Earth, T" = 1 day = 1 day × 24 hr/day × 60 min/hr × 60 s/min = ‭‭86,400‬ s

So, ω" = 2π/T"

= 2π/86,400‬ s

= 7.272 × 10⁻⁵ rad/s

Since ω' = 4.132 × 10⁻⁷ rad/s << ω" = 7.272 × 10⁻⁵ rad/s, the sun would appear to move more slowly across Mercury's sky.

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3 years ago