help with these problems pls

1. What are two important quantum-mechanical concepts associated with the Bohr model of the atom (2 points)? 2. What are two important refinements resulting from the wave-mechanical atomic model (2 points) 3. Why covalent materials are less dense than metallic or ionic materials (2 points)? 2 4. Write down the electron configurations for the following atoms/ions and answer the follow-up questions (14 points in total; 4.1-4.5: 1 point for each question; 7 points for 4.6; 2 points for 4.7): 4.1. P (15) 4.2. p. 4.3. Sn (50) 4.4. Sn" 4.5. Write down the molecular formula for the compound (Tin Phosphide) that Snand Plcan form. 4.7 Based on question 4.6, what are the dominant and minor bonding types in Tin Phosphide? 4.6 Compute the ionic percentage (IC%) of Tin Phosphide. Electronegativity of the Elements H nodata 3 555 58 52 15