francium , in the Periodic table the atomic radius increases from top to bottom in a group, and decreases from left to right across a period. making helium is the smallest element, and francium the largest.
Electron configuration
an element A has 3 shells and has 3 valence electrons
so electron configuration of A: 1s², 2s², 2p⁶, 3s², 3p¹
will tend to lose 3 electron to form a cation: A³⁺
a. Nitrate of A
A(NO₃)₃
b. Chloride of A
ACl₃
c. Oxide of A
A₂O₃
Answer:
Explanation:
The nuclear equation from which you have to identify the missing element is:
- ²³⁹₉₄ Pu + ¹₀n → ___ + ¹³⁴₅₄Xe + 3 ¹₀n
The superscripts to the left of each chemical symbol are the mass number of the atoms (number of protons plus neutrons) and the subscripts to the left of the chemical symbols are the atomic numbers of the atoms (number of protons).
Thus, such equation must be read as "an atom of plutonium-239 is bombarded with a neutron and produces one atom of an unkwon element, one atom of xenon-134, and 3 neutrons".
To find the identity of the missing element you must do two balances: mass number and atomic number.
Mass number:
Hence, the mass number of the missing element is 103.
Atomic number:
Hence, the atomic number of the missing element is 40.
In a periodic table you can find that the element with atomic number 40 is zirconium, Zr.
Thus, the identity of the missing isotope is zirconium-103, ¹⁰³₄₀Zr.
And the complete equation is:
- ²³⁹₉₄ Pu + ¹₀n → ¹⁰³₄₀ Zr + ¹³⁴₅₄Xe + 3 ¹₀n
Answer:
ρ = 7.9 g/mL
Explanation:
The total volume (21.36 mL) is equal to the sum of the volume of iron and the volume of water.
V = V(water) + V(iron)
V(iron) = V - V(water)
V(iron) = 21.36 mL - 20.10 mL
V(iron) = 1.26 mL
9.9 grams of iron occupy a volume of 1.26 mL. The density (ρ) of iron is equal to its mass (m) divided by its volume (V).
ρ = m/V
ρ = 9.9 g / 1.26 mL
ρ = 7.9 g/mL
