Answer:
30, 50
Explanation:
Hello,
In this since an element's atomic number is equal to the number of protons in its atom, we can infer that selenium's atomic number is 30. Moreover, due to the fact the the neutrons are equal to the atomic mass minus the atomic number or the number of protons, by knowing the number of neutrons we compute the atomic as follows:
Thus, answer is 30, 50.
Best regards.
U-238
The number besides the U means its total molar mass. The molar mass of this element is 238
Molar mass= protons + neutrons
This means that 238= 146 + protons
Do 238 - 146
Answer is 92
Answer:
The value of the heat capacity of the Calorimeter 
= 54.4 
Explanation:
Given data
Heat added Q = 4.168 KJ = 4168 J
Mass of water 
= 75.40 gm
Temperature change = ΔT = 35.82 - 24.58 = 11.24 ° c
From the given condition
Q = 
ΔT + ΔT
Put all the values in above equation we get
4168 = 75.70 × 4.18 × 11.24 + × 11.24
611.37 = × 11.24
= 54.4
This is the value of the heat capacity of the Calorimeter.
Answer: A)There is a high ratio of energy to cost
Positives:
A Chunk of Uranium can power a city a lot longer than a chunk of coal.
It also does not contribute to pollution since what comes out of the tower is steam.
Negatives:
It is very expensive to build and maintain a nuclear power plant at first so investors whom want money up front are more reluctant to loan money for one.
If the plant does melt down it is very bad for the enviroment and its people, for example Chernobyl Nuclear Power Plant in the Ukraine will not be able to be lived in for approximently 20,000 years.
The elements in the periodice table are not listed in alphabetical order, because the arragement in rows (periods) and columns (groups or familes), in increasing order of atomic number (number of protons of the atoms) permits to explain similarities among the elements, trend in some properties, and even predict properties of unknown elements.
For example, the elements of the first group (family), called alkaline metals, all have 1 valence electron, have similar physical properties (ductibility, malleability, luster, thermal and electricity conductivity), react in similar way with water, show a trend in the atomic radii and in the ionization energy.
You can tell similar stories for other groups like, alkalyne earth metals, halogens and noble gases.
You can also tell trends in electroneativities, and atomic radii, for a row of elements, as per the order they are in the row.
So, the current array resulted very helpul for chemists to explain and predict the behavior and properties of the elements.
