False. elements in the same period have the same number of shells while elements in the same group have the same number of valence electrons.
atomic mass=percentage of isotope a * mass of isotope a + percentage of isotope b * mass of isotope b+...+percentage of isotope n * mass of isotope n.
Data:
mass of isotope₁=267.8 u
percentage of isotope₁=90.3%
mass of isotope₂=270.9 u
percentage of isotope₂=9.7%
Therefore:
atomic mass=(0.903)(267.8 u)+(0.097)(270.9 u)=
=241.8234 u + 26.2773 u≈268.1 u
Answer: the mass atomic of this element would be 268.1 u
Answer:
the answer is C) sharing
Explanation:
positive ions & negative ions form when atom s lose or gain electrons. Covalent bonds form when atoms share electrons.Metallic bonds form by the attraction of metal ions and the electrons around them. Covalent compounds form when atoms of elements share electrons.
Answer:
- There will be 1.23 moles of helium in the balloon at STP
Explanation:
1) <u>Initial conditions of the helium gas</u>:
- V = 20.0 liter
- p = 1.50 atm
- T = 25.0 °C = 25.0 + 273.15 K = 298.15 K
2) <u>Ideal gas equation</u>:
- pV = n RT
- p, V, and T are given above
- R is the Universal constant = 0.0821 atm-liter / ( K - mol)
- n is the unknown number of moles
3) <u>Solve for n</u>:
- n = 1.50 atm × 20.0 liter / (0.0821 atm-liter /k -mol ×298.15K)
4) <u>At STP:</u>
- STP stands for standard pressure and temperature.
- The amount (number of moles) of the gas will not change because the change of pressure and temperature, so the number of moles reamain the same: 1.23 mol.
