A line chart connects observations in their worksheet order. It works well for measurements taken at equal intervals, such as weekly shipments or monthly hours. Put the periods in the first column and select them with the value columns. Choose Line with Markers when the reader needs to see every recorded observation.
A zero is a real observation at the baseline. A blank is missing data and leaves a gap in the line. Keep that distinction when a sensor stops reporting or a team has not submitted its figures. Joining across the gap would suggest a measurement you never made.
A scatter plot has a numeric horizontal axis. Use it when distances between x values matter, such as elapsed minutes at irregular intervals. A line chart treats those same labels as equally spaced categories. Chart Design > Select Data lets you correct the source or switch rows and columns when Excel groups the observations the wrong way.