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3 years ago

Which elements have two valence electrons?

Chemistry

1 answer:

lora16 [44]3 years ago

7 0

Answer:

Magnesium

Explanation:

Magnesium is in group 2 of the periodic table. The group in which an element is found in tells us the number of valence eletrons it has.

HOPE THIS HELPED

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3 years ago

Thorium-234 has a half-life of 24.1 days. How many grams of a 150 g sample would you have after 120.5 days?

chubhunter [2.5K]

Answer:

8.625 grams of a 150 g sample of Thorium-234 would be left after 120.5 days

Explanation:

The nuclear half life represents the time taken for the initial amount of sample to reduce into half of its mass.

We have given that the half life of thorium-234 is 24.1 days. Then it takes 24.1 days for a Thorium-234 sample to reduced to half of its initial amount.

Initial amount of Thorium-234 available as per the question is 150 grams

So now we start with 150 grams of Thorium-234

$150 \times \frac{1}{2}=24.1$

$75 \times \frac{1}{2} =48.2$

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$17.25 \times \frac{1}{2} =96.4$

$8.625\times \frac{1}{2} =120.5$

So after 120.5 days the amount of sample that remains is 8.625g

In simpler way , we can use the below formula to find the sample left

$A=A_{0} \cdot \frac{1}{2^{n}}$

Where

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n = the number of half-lives that pass in a given period of time.

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3 years ago

Which of the following statements is true? Choose one: A. Bronze was used as early as 4000 B.C.E. to replace less-desirable iron

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Answer:

B.Bronze is harder than copper, so it retains a cutting edge sharper than that of copper.

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The importance of bronze in the history of the human kind can not be only measured in the durability but the help that it provided to our ancestors, the things they were allowed to do once they dicovered how to mold it, and the tools that they produced and made many every day tasks easier for them and the ability of bronze to mantain the cutting edge longer than copper was one of the main reasons why it took its places in the fabrication of many tools.

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